Why do the Americans write the date in a different order? Did the Twin Towers come down on 9th of November? Military equipment designations are - as others have already written - based on ease of cataloging stores. What is "it" followed by descriptions of what sort of "it" it is. When you think about it properly, it makes alot of sense. What is it or what do you want? An armoured vehicle. What type of armoured vehicle is it / do you want? An RE one. As opposed to... What is it or what do you want? A Royal Engineer What type of Royal Engineer is it / do you want? An armoured vehicle one.