Information Requested on Boy Entrant Service Numbers v. Training Locations, last 3 and Entries.

Do all ex-boy entrants have service numbers starting .19…..? (I know the letter at the front was introduced in the digital age in mid 1964).

How were the numbers allocated to training stations such as Hereford, St. Athan, Cosford, Locking, Halton, et c? Would it be possible for instance to identify the training camp from the allocated service number last 3 or vice versa?

My particular interest is in Numbers is .1944… which, at least at St. Athan, was the 43rd Entry. Would the “1944…” also be part of the 43rd Entry at other boy entrant bases such as Hereford and Cosford? Would the “last 3” help to identify the base and the entry. My Flight and Squadron for instance numbered .19442.. (mid range) but where and which were lower 19442.. and the greater 19442.. service numbers?

If any reader has a .19442.. number perhaps you can give me your training base and your number (or range, if not). I have a feeling that 44th entry, St. Athan, also had 19442.. numbers. Maybe you can let me know?

Don, ex D Flight 2 Sqn. 1 Wing RAF St Athan.