Sherman 17-pdr (Firefly) - conversion restrictions

Discussion in 'Weapons, Technology & Equipment' started by Gary Kennedy, Sep 18, 2020.

  1. ceolredmonger

    ceolredmonger Member

    Agreed, however, imagine in the winter of 44/45 watching the Brigade fitters turn up to weld extra armour on only half the vehicles in your troop. It may have been small, specific areas but it was something. My friend, as the gunner, remembered that the kit included the turret 'cheek' armour as well as the three hull and two small glacis plates however it was all or nothing and Sherman 17pdr was exempt.
     
  2. ceolredmonger

    ceolredmonger Member

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  3. Ewen Scott

    Ewen Scott Well-Known Member

    Its a Sherman Ic Firefly (note the spacing between the wheels). Conversion of this model began after the initial Vc and all seem to have had the add on armour kit judging by the photos. Only a couple of Ic were in service by the end of June 1944 with the Polish Armoured Division.

    I was looking through Mark Hayward’s Firefly book and while the early Vc that went to Normandy did not have the additional armour kit, by August Vc with the armour kit were beginning to be photographed.
     
  4. Don Juan

    Don Juan Well-Known Member

    I did come across this subject in my vast compedium of archive documentation, and from what I recall the key aspect that made a Sherman suitable for 17 pounder conversion was the hull length. The M4A4 had a longer hull than earlier Shermans - see the diagram below:

    Sherman Hull Types.jpg

    If the Sherman I Composites built by Chrysler also incorporated the long hull, this would lend weight to this assertion. Exactly why the long hull was needed was not explained, but it may have been necessary to balance out the forward weight of the gun, or to even out the increased ground pressure of the tank, or to provide more room for stowage etc.

    I can't remember for the life of me where I saw this info, so you'll have to wait until I chance upon it again before I can post the original documentation up here.
     
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  5. Ewen Scott

    Ewen Scott Well-Known Member

    The M4A4 needed the longer hull due to it being designed around the Chrysler Multibank engine. The only other version with the long hull was the Chrysler built M4A6 with the Caterpillar D200A engine. Only 75 of this later variant were built and none saw service outwith the USA.

    After building 7499 M4A4 between July 1942 and Sept 1943, Chrysler went on to build 1676 M4 Composite/Hybrid between August 1943 and Jan 1944. After that it became the sole source for the M4(105), built Feb 1944 to Mar 1945, and M4A3(105) from May 1944 to June 1945. After Jan 1944 it was only building new 105mm gun tanks. As previously stated the 105mm gunned tanks were not suitable for conversion to Fireflies.

    From late in 1943 any spare production capacity at Chrysler was taken up with remanufacturing Sherman tanks built in earlier years, in particular some 1600 M4A4, delivered to the US Army and used for training purposes in the USA. These were then delivered to Britain. These were brought up to the latest production specs, including fitting the armour patches. Many later became Fireflies.

    Dimensionally there was no difference in hull length between the welded hull M4 as built by several manufacturers and the M4 Composite. In British hands they were known as the Sherman I and Sherman I Hybrid respectively and no distinction was made between then unlike the separate designations given to the M4A1, A2 and A3.

    Fireflies were converted initially from the long hull M4A4 Sherman V because in early 1944 it was the most numerous Sherman version planned for service with armoured units in North West Europe. When suitable chassis became hard to find attention turned to the available Sherman I chassis.

    For all things Sherman the best sources are
    Sherman minutia homepage
    https://www.amazon.co.uk/Sherman-Hi...an+by+hunnicutt&qid=1601498795&s=books&sr=1-1

    June 1944 tank strengths here 21st Army Group Tank Strengths - June 1944
     
    Last edited: Sep 30, 2020
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  6. Don Juan

    Don Juan Well-Known Member

    Well, the first link that you posted states this:
    So this may have been the deciding factor.
     
  7. Ewen Scott

    Ewen Scott Well-Known Member

    The reasons for the lack of suitability of the M4A1, A2 and A3 as Firefly conversions must remain pure speculation as no research thus far has revealed any reason stated in official documents. Even Mark Hayward considers his book, the most detailed on the Firefly so far produced, as a work in progress as certain areas of Firefly development remain a mystery even to him.

    The M4A3 is the most explainable in that only a handful were ever supplied to Britain.

    The M4A1 is the least explainable. Mechanically identical to the M4, the most frequently quoted reason, which I gave in my earlier post, is the rounded hull shape of the cast hull. But to me, on more detailed examination of the conversion work, hull shape doesn’t seem to be an issue as any ammunition held in the sponsons of the basic 75mm M4/M4 Hybrid was moved, in the Firefly conversion, below sponson level, which could equally have been done AFAIK on the M4A1 due to the identical mechanical layout.

    The welded hull M4A2 had an engine equally as powerful as the M4A4, and more powerful than that in the M4/M4A1, which theoretically would make it more suitable to cope with the heavier Firefly conversion. It was the second most numerous version supplied to Britain. But less were supplied in 1944 than M4/M4 Hybrid or M4A4.

    My personal view (guess) is that it came down to availability in 1944 especially when you look at the various versions supplied to Britain and at what time and to which theatre, during the war. M4A4 initially as the most numerous version available on hand in U.K. vehicle parks in late 1943 when conversions began. Then, as numbers of M4A4 available from stock fell off, M4 from supplies of new tanks (especially Hybrids) supplied in 1944, and then switching back towards (but not exclusively) to the M4A4 from the stocks of remanufactured tanks supplied in 1944.
     
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  8. Ewen Scott

    Ewen Scott Well-Known Member

    There is a lot of data in the appendices of Armoured Thunderbolt about stocks of British/Canadian Shermans on hand in 1944/45 in NWE that can sometimes, depending on your browser, be seen here - Appendix C
    https://www.amazon.co.uk/Armored-Thunderbolt-Sherman-Tank-World/dp/0811704246

    Holdings June 1944 by model - in units/tank parks /total

    M4 223/52/275
    M4A1 192/50/252
    M4A2 340/150/490
    M4A4 794/178/972
    M417pdr 2/0/0
    M4A4 17pdr 316/24/340
    DD 502 (mostly M4A4 but includes 80 M4A1 from US Army stocks)
    Crabs 180/45/225 (All conversions from M4A4)
    Totals 2298/750/3048.

    The M4A4 remained the predominant 75mm Sherman throughout the campaign in NWE with Firefly versions growing to 224/231/454 in May 1945.

    In contrast the number of 75mm M4s fell but M4 17pdr rose to 485/295/780 by May 1945.

    Sherman shipments to Britain by year 1942/1943/1944/1945/total and model were as follows:-

    M4/M4A1 268/752/2018/90/3128
    M4A1(76) 0/0/1330/0/1330
    M4A2 456/4083/501/8/5048
    M4A2(76) 0/0/0/20/20
    M4A4 147/5385/1631/5/7168
    M4(105) 0/0/488/105/593

    Deliveries of M4/M4A1 are not broken down as the US considered them identical and interchangeable. Only 43 M4 and 148 M4 Hybrids were new build in 1944.

    All the M4A2 we received were small hatch versions built before the end of Nov 1943.
    All the M4A4 were built before the end of Sept 1943.

    When you sit down and analyse production of the various models supplied to Britain under Lend lease v the timing of the deliveries, it is hard not to conclude that most of the M4A1/A2/A4 supplied in 1944 had to be remanufactured tanks. The only definite exception is 80 M4A1 DD tanks supplied from US stocks just in time for D-Day.

    The M4 Composite/Hybrids were amongst the last M4 built and would have been new build deliveries to Britain, which is probably why they feature so strongly amongst Sherman Ic conversions. But only 1976 of these were built and not all came to Britain as evidenced by the photos available. As they were not treated as a separate Sherman type in the records it is impossible to tell how many we received.
     
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  9. Don Juan

    Don Juan Well-Known Member

    As far as I'm aware no M4A2's were supplied to the armoured divisions in NWE as gun tanks. Do you know why this is?

    Were they reserved for other theatres e.g. ME, CBI etc.? I'm wondering whether the RAC was attempting to standardise on petroleum for NWE, so any diesel engined vehicle was automatically considered unsuitable. The entire subject of getting petroleum over to the Continent for such a large army was a big issue, hence PLUTO etc., so the complicating factor of supplying diesel as well might have made any compression ignition vehicle an automatic no-no.

    Trying to think of a diesel AFV that was used in NWE...

    Edit:- Just remembered that a lot of British M4A2's were passed on to the Soviets precisely for fuel conformity reasons...
     
    Last edited: Oct 1, 2020
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  10. Chris C

    Chris C Canadian

    M10s and eventually Valentines and Archers were diesel powered, but of course none would have been in RAC regiments. From a divisional point of view though most of the M10s in NWE would have been in the anti tank regiments in the armoured divisions.

    But no one would have wanted a mix of diesel and petrol powered tanks in the same unit.
     
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  11. Don Juan

    Don Juan Well-Known Member

    Thanks Chris.

    I'm wondering if this whole thing is a mystery that isn't a mystery. If the M4A2 was being excluded from NWE generally (there were no Crab or DD conversions of M4A2's either) then this would explain why there were also no Firefly conversions of it. You did not need Fireflies in e.g. Burma. There also did not need to be any express instructions to exclude M4A2's from Firefly conversion because at the time any fool would have known that they were not going to NWE in any case.

    Therefore the limited capacity for Firefly conversions was concentrated on the most common verson of petrol Sherman that was available - firstly M4A4 and then M4A1 Hybrid. The reason there were no M4/M4A1 cast hull conversions may have been simply that towards the end of the war these were too thin on the ground through being written off or overseas etc.

    If it's a mystery that isn't really a mystery, this would also explain the lack of documentation around it.
     
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  12. Ewen Scott

    Ewen Scott Well-Known Member

    The US Army very quickly decided it didn’t want the diesel engined M4A2, deciding to standardise on petrol engined M4/M4A1 in 1942/43. So the main users became the US Marine Corps (493 where diesel was readily available from the USN), Britain (5038), France (383) and the USSR (2040). In fact the USSR so liked the Diesel engine that in 1944/45 virtually the entire production run of M4A2/M4A2(76mm) was destined for them.

    Britain was receiving M4A2s in quantity before it began to receive M4A4 (look at the numbers lend leased in 1942 for example). The main active theatre was the Med so inevitably many early M4A2 went there and there is a preponderance of that model in British / Canadian / New Zealand / South African / Polish armoured units there from early 1943. Over 1100 were reported on hand in Nov 1943 for example v some 450 M4A4. As well as Africa / Italy there was also the 31st Indian Armoured Div which spent its war in Iraq /Iran / Persia which got Shermans in Nov 1943 which AFAIK were M4A2.

    You will get some feel for the mix of models in the Italian theatre from a study of the Sherman Minutia site.

    It is interesting to note that the 5th Canadian Armd Div was sent to the Med without tanks in late 1943, taking over those war weary vehicles previously used by 7th Armd Div which were mostly M4A2. Then, when it got new tanks in 1944, these seem to have been M4A4 which it then took to NWE when transferred there in Feb 1945 as part of Operation Goldflake. In some ways this reinforces the idea of M4A2 deliveries slowing down as 1943 went on while M4A4 deliveries to the Med increased. Another area of interest to research.

    In the Far East there were only 3 armoured brigades and only one of those, plus a regiment in another, used Shermans operationally (the Lee/Grant remained in front line service in that theatre until the end of the war) and these were M4A4 Sherman V. Some M4A1 and M4A2 were however reported to be in theatre from the 600+ sent there. 126 M4A4 from British stocks were passed onto the Chinese in 1944. By Aug 1945 there were also some M4A2 DD.

    As you will have seen while the M4A2 was not used by the armoured divs in NWE, it was used by three of the independent armoured brigades and for the Rhine crossing it was the M4A2 DD version that predominated in British DD units.

    Fuel type may have played some part in deciding how to equip the armoured divisions in NWE. Clearly easier if everything in the unit is petrol powered. Less relevant in 1942/43 perhaps where a diesel powered Sherman is better than a petrol powered British tank or nothing. Then, having so equipped a unit, it is easier to try to maintain that type so far as possible. Other than that I see the matter as one of the timing of availability of each model and the actual warfighting demand at the time.
     
  13. Don Juan

    Don Juan Well-Known Member

    A few things to note with regard to Monsieur Kennedy's original post:

    The thing to note here is that the R.M. Weeks quoted here is Lieutenant-General Ronald Weeks, the Deputy Chief of the Imperial General Staff (DCIGS) at the War Office. As such he was not from the Ministry of Supply and was not directly involved in Firefly development so his information does not come straight from the horse's mouth. It is possible that Weeks was informed by somebody at the MoS who did know what was going on (e.g. Claude Gibb or Bill Durrant or Robert Micklem) that certain models of Sherman were unsuitable for Firefly conversion, and he presumed that this was due to the mounting of the gun, even if it may not have been.

    I'm not suggesting Weeks is necessarily wrong, but that a degree of scepticism is necessary with his statement in a way it wouldn't be if it had come directly from e.g. Claude Gibb.

    The issue here was the the US Army had grossly underestimated its required tank reserves for NWE, and so its losses were starting to eat into its tank availability by the third quarter of 1944. IIRC the US had provided itself with 66% reserves while the British had budgeted reserves at something over 200%. This had the consequence that during the last quarter of 1944 the Americans drastically cut their M4 supplies to the British in order to redirect them to their own armies, and it was this that caused the "lack of suitable Shermans for conversion to 17pr,"

    Was the M4A2 standardised across any of the independent armoured brigades from June 1944, or was it a late 1944 fill in? I'm wondering if the M4A2 had to be issued in NWE due to the restriction of US M4 supplies I mentioned above. I'm also wondering whether the M4A2 DD was originally intended for other theatres (i.e. Italy) and again had to be redirected to NWE due to late -'44 US supply restrictions.
     
  14. Ewen Scott

    Ewen Scott Well-Known Member

    Re the armoured brigades, take a look at the table I linked to in a previous post. In June 1944 3 brigades had M4A2 Sherman III as main equipment alongside Sherman Vc Fireflies and Sherman II and V DDs. So they were not late 1944 fill ins.
    21st Army Group Tank Strengths - June 1944

    Right from the start the M4A2 figured in the DD plans. RAC reports from late 1943 show a requirement for 100 M4A4 and 593 M4A2 conversions. By mid 1944 orders had been placed for 400 M4A4 and 293 M4A2 conversions and that was what was built. The Sherman V DD came first in time for D-Day with the Sherman III DD being the later builds. All had been completed by the end of 1944. British plans for 1945 called for 300, later reduced to 200, more for use in the Pacific to be built from Sept 1945. But these would have been a new version built on the M4A2(76)HVSS chassis. All the M4A1 DD used by Britain came from the US Army conversions in early 1944. See here for more info
    Duplex drive Sherman tanks
    https://www.amazon.co.uk/Swimming-S...imming+shermans&qid=1601555276&s=books&sr=1-1

    Only 7th Hussars used M4A2 DD operationally in Italy, in April 1945 to cross the Po. One regiment, 25th Dragoons got them in the Far East from mid 1945, but some of its tanks may have come from Italy.

    By the end of 1944 there were no more M4A4 left in the pipeline to supply to Britain. Production had stopped in Sept 1943, and the Chrysler remanufacturing programme ran out of vehicles in late 1944.

    Total built - 7499
    To France in 1943 - 274
    To Russia - 2
    Remaining - 7223
    To Britain (as new build and remanufactured) - 7168
    Balance of 55 held in USA for various purposes.

    Of the other 75mm models only the M4A2 (for Russia and the USMC, produced until May 1944) and the M4A3 versions were produced after Jan 1944 and the US Army wanted all of the latter for itself. So the only other source was remanufactured tanks from training establishments in the US, but as noted, the US needed as many tanks as it could get. Britain took, but didn’t really want, the M4A1(76) although the 1st Polish Armd Div was re-equipped with them in Autumn 1944 along with Fireflies and some were issued to units in the Italian theatre.

    While Fireflies might have been a wasting asset from May 1945, Britain was already producing the Comet with the 77mm gun. With production starting in Sept 1944, 1200 had been produced by the end of the war. It had already re-equipped the 29th Armd Brigade in 11th Armd Div, and 22nd Armd Brigade in 7th Armd Div had begun to re-equip by the time it went to Berlin in July 1945. That process would free up Fireflies for Sherman units had the war gone on longer. So I’m not sure there would have been a problem.
     
  15. Don Juan

    Don Juan Well-Known Member

    I seem to remember from somewhere (Buckley?) that the independent armoured brigades were basically instituted due to a shortage of Churchills i.e. they were originally intended to be tank brigades. It does seem that the M4A2 gun tank was an unfavoured tank for NWE, and was only included in formations when shortages demanded it.

    I think the M4A2 would be the natural choice for a DD tank as its twin engines would be more appropriate to drive the twin propellers. So from 1943 planning, it would make sense to reserve M4A2's for DD conversion, and hence preclude them from Firefly conversion.

    The British were certainly expecting to convert an armoured division to 76mm M4's over the winter of 1944/45, as the original plan was for 7th Armoured Division to take the Comet, and one other AD to convert to 76mm M4's. I had presumed these were going to be M4A3's but I haven't looked at this in detail. In the event, 7AD were forced to keep their Cromwells and 11AD took the Comets.
     
  16. Ewen Scott

    Ewen Scott Well-Known Member

    Re the final para. Is that one armoured div to convert to 76mm gun Shermans (I.e. the 1st Polish) or one British Armd div in addition to the 1st Polish?

    The final allocations of M4A1(76) to Britain (of the 1330 total) were 150 per month in Aug/Sept/Oct 1944 forming 34/35/46% of Sherman deliveries in those months. By the end of the year 418 were in Italy (incl 65 in reserve) growing to 484 by the end of June 1945. The 1st Polish started receiving them on 20 Nov 1944 and got 60 by the end of the year, with 180 received by the end of the war. At the same time the Poles had 40 Fireflies.

    No Shermans at all were delivered for British use in Nov & Dec and only 228 in 1945 (that includes 105 M4(105) support tanks (again not really wanted). This was a big issue given that 500-1000 were delivered monthly between Feb and Aug 1944. So US tank supplies had effectively dried up by the end of 1944. Just as well the Comet was ready and the Centurion in prospect.

    Things were so bad for the US Army in NWE tank wise that on 26 Dec 1944 they requested 500 tanks be supplied to them from British stocks. In Jan 1945 352 were supplied in answer to that plea including 87 M4A1(76). The rest were whatever could be scraped together in a hurry from various depots on the continent and were a mix of M4/M4A1/M4A2/M4A4.

    The US Army only began deploying the M4A1(76) in July 1944 immediately prior to the Operation Cobra Normandy breakout, despite having had a couple of hundred available in Britain from April. M4A3(76) followed in Aug. Both versions remained in production until July and April 1945 respectively.

    Such was the demand for the M4A3(76) particularly the HVSS version, that plans existed to ship spare tanks direct from Europe to the Philippines in summer 1945 to try to re-equip tank units in time for the invasion of Japan.
     
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  17. Don Juan

    Don Juan Well-Known Member

    My understanding is that it was one British armoured division in NWE as well as 1st Polish. There was a general expectation in 21 AG in late 1944 that 76mm armed Shermans would soon become standard equipment - I'll see if I can pull out some relevant info.
     
  18. Ewen Scott

    Ewen Scott Well-Known Member

    Forgive me but I'm a bit sceptical how, from 1330 tanks, there could have been 2 divisions planned in NWE with M4A1(76) in 1945 given the 200+% reserve you quoted in post #33.

    UE in 1944 for an armoured brigade in an armoured division (gun tanks only excluding recce tanks, CS, ARV, AA, OP, bridgelayers etc and the armoured recce regt) = 184
    Less Fireflies (1 per troop) = 36
    Gun tanks in division = 148
    200% reserve = 296
    Total tanks required per armoured division = 444

    2 divisions = 888

    Armoured Recce Regts in British and Polish armoured divisions, but not the Canadians, got Cromwells. Replace those with M4A1(76) and you need another 55 gun tanks per division less an allowance for Fireflies.

    Available by end of Oct 1944 = 1330
    Less with Med units by Dec 1944 = 418 (353 with units and 65 in depots so ignores additional reserves to cover attrition up to the 200+% requirement)
    Balance for NWE = 912

    So the NWE requirement is only just covered before considering the emergency transfer of 87 to the US Army in Jan 1945 and the need to allocate more to Italy to build up the required reserve there (potentially up to 641 (353x2 less 65 already held) based on Dec 1944 issues to units). It gets a bit better if you can guarantee 2 Fireflies per troop as the requirement. Even if you cut the reserve to 100% there is only just enough. 148x 2 divisions + 353 for Italy = 649 + 100% reserve = 1298 tanks from 1330 delivered.

    As I said, everything I've read suggests that Britain took the M4A1(76) because there was very little option. That is one reason why they were happy to take remanufactured tanks in 1944, to keep the 75mm version. And the last allocation was made in Oct 1944. I've not seen any indication of where any extras might have come from given US demand.

    From my research the remanufacturing programme generated the following:-

    M4 - 8/44-4/45 - 795 (plus 163 as recovery vehicles)
    M4A1 - 8/44-5/45 - 2259 (plus 1001 as recovery vehicles)
    M4A2 - 4/44-11/44 - 535
    M4A3 - 8/44-5/45 - 681 (plus 298 recovery vehicles from the 1610 Ford built tanks produced in 1942/43 retained in USA for training)
    M4A4 - 12/43-10/44 - 1610

    Like the M4A4, the M4A2 remanufacturing programme seems to have almost exhausted the supply of available tanks by the time it finished. Given the numbers it looks like most of these would have come to Britain as Lend Lease in 1944.

    I look forward to any additional information you might have.
     
  19. Gary Kennedy

    Gary Kennedy Member

    I did put together some numbers a long time ago, mostly gleaned from the few 21AG AFV returns I was able to find copies of.

    UE for 76-mm armed Shermans was shown as 148 before dropping to 94. I would have to check back to be certain but I recall the 148 figure appears in the Jan/Feb 1945 returns, and drops to 94 either end Mar or early Apr 1945. The 21AG 17-pr UE (circa Jan/Feb45) was 660, which allocates as 30 per Br/Cdn Sherman equipped Armd Regt, and 15 in the three Cromwell Regts of 22 Armd Bde. That leaves 45 not in Br/Cdn units, which added to the 148 76-mm tanks makes 193, which is the number of cruisers in an Armd Bde (three Regts on 61 each plus 10 on Bde HQ) and sufficient to fill out the Polish Armd Bde.

    The final picture was a UE of 795 17-pr and 94 76-mm, from the Mar/Apr45 timeframe. With all the Br/Cdn Sherman equipped Armd Regts on 24 17-pr (still two per Tp but back to four Tps of four, rather than five Tps each of three tanks), that leaves 99 17-prs. With the Polish Armd Bde on a reduced 166 cruisers, they would need 72 17-prs and 94 76-mm tanks to equip Bde HQ (10 tanks) and three shortened Regts of 52 tanks each (so three Tps, each of two 76-mm and two 17-pr, with all Sqn and RHQ tanks as 76-mm). The Czech Indep Armd Bde looks to have been authorised the remaining 27 17-pr tanks, and was likewise down to 52 cruisers per Regt, with the balance of 121 75-mm and 18 CS Cromwell tanks not in Br formations.

    Gary
     
  20. Osborne2

    Osborne2 Well-Known Member

    I have been looking a little into Polish army strength in 1944 in relation to France. I have picked up that there was some doubt whether the 1st Polish AD would go to Normandy as manning levels were so marginal. Some anecdotal references seem to indicate that the Division went scouring some POW cages in France to enlist Poles who were forced into the German army before D Day. 89,000 such men went over to the allies in Italy and France by one means or another, either deserting and risking being shot, or captured and freed. By the time of the reductions for the Czechs and Poles tank UE's, perhaps the early losses in KIA/MIA and WIA may have made them unable to replace the trained men? I suspect tankers cannot be made overnight. It's just a thought amnd perhaps a Polish specialist or someone with access to War Diaries knows.
     

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