There were plenty of what were known as 'LOST OR INDISTINCT SERIAL NUMBERS' and the worst offenders were No4's, 5's No8's and Stens ......., all made at the dreaded Fazakerley. If 80 rifles went into the main Field or Base workshop for overhaul, all numbered and recorded on the AFG 1045, then 80 would be returned. If a number was lost or indistinct then those would be numbered to suit the numbers on the AFG 1045 and returtned to the unit.
There was another more troublesome method but where there's a will, there is always a simple way. It looks to me like this was the case here. Indistinct number match to another on the working documentation. Everyone is happy.
As a matter of interest, there were many hundreds of Fazakerley No8 rifles that came in, serial numbered CRxxxx from the VAOS number that was marked more clearly than the serial number
If my memory os right, the AA marking is an area code relating to the Indian reserve forces... Alambarahad was the suggestion by our ever helpful Indian Army Liaison Officer. A bit like the old butt marking discs