Engine 90625 was from the very last contract (S6150) in 1944 and was fitted in frame 73625 which was given census number C6112625. See how the last digits 625 follow on in this series of numbers. Ron
Blocks of Census numbers were not allocated to units, although quite often numbers close to each other arrived at the same place. All machines from this contract were delivered to RAOC Chilwell, theoretically at 1400 per month commencing November 1944. Although originally for 10,000 bikes, (Frames 73000 - 82999 and engines 90000 - 99999) it was curtailed at 6089 so the last frame number was 79088. Presumably the highest engine was 96088.
According to the Chilwell records, the census numbers issued were C6112000 - 6117286, 288-309, 311-332, 334-6118091...no explanation for why 6112310 and 6112333 were not used...but they may well have stayed with the matching last two digits (25) that seem to have featured across all makes by this time.
It is likely that the deliveries were delayed and the bike may well still have been at Chilwell at the end of the war - they were building up huge stocks for a war in the Far East that was expected to last another two years...it could have been sent anywhere after that...and of course not only Scottish infantry regiments were stationed in Scotland.