Steve Tee. Your Dad effectively joined a 'retained' type of reserve - The territorials were civilians volunteering to train to serve if required. They got (and still get) their 'bounty' and payment for training and skills courses which were provided under King's Regs. however they were not considered 'With the Colours" until 'Mobilisation'. Army form E635 is the individuals notification that the unit had been mobilised and they were to report for duty - they were in the Army now, not part time. The formal time and place goes back to this being an actual muster and for them to march off to war. In most cases in the 2nd World War there was a day or two's grace whilst they located strays and finished admin. - such as changing from reserve stores to regular. Not turning up was a breach of terms and could be considered desertion. There is a Transfer from the Regular Reserve equivalent.