A prefix of AK would indicate ROF Maltby for 1943 (from Stratton's text).
Not quite. You are right on the factory, but wrong on the identifyer. All of the factories used the letter prefixes like that. The first # in the serial # lets you know where it was produced. Here is a (long) quote from Skennerton's website
http://www.enfieldcollector.com/index.html. I've bolded the main point.
No.4 and No.5 rifle serial numbers can readily identify manufacturers. British No.4 rifles have five numbers, usually after one or two letter prefixes.
The same letter prefix(es) were used by Maltby, Fazakerley & BSA Shirley, A to Z then AA, AB to AZ, then BA to BZ, CA to CZ &c. Maltby rifle serial numbers commence with a number '1', Fazakerley with a '2' and Shirley with a '3', e.g. 1###x for Maltby, 2###x for Fazakerley and for Shirley, 3###x, after the letter prefix. Late Shirley numbers then supposedly ran A4000 to A7999 and with PS prefixes at the very end of production. Post-war Fazakerley No.4 rifles had PF letter prefixes. The only exception to the 5-number sequence for No.4 rifles was the initial BSA Shirley production which ran from 0001 to 9999 then went with A to Z prefixes (A0001 to A9999 to the Z prefix) and some early dual letter prefixes (e.g. AT 0303), but then went over to A30001, &c. So early M47C No.4 rifle numbers could be confused with the Jungle carbine in having four rather than five numbers.
Long Branch (Canada) serial numbers incorporate an 'L' in the serial number while US Savage numbers include an 'C' in a similar relative position amongst the numbers. Both of these No.4 rifle series commenced with 0L1 and 0C1 respectively.
No.5 Jungle Carbines only have 4 numbers, the Shirley carbines have BB to C? prefixes, last production was post World War 2. The Fazakerley jungle carbines ran from FE1 to FE1000 initial production, then with no letter prefix, followed by A1 to A9999 through Z9999.
