I think the 'code' on the wrist is the Army & Navy CSL (serial) number.
Often found on the trigger guard bow instead.

Nice rifle for sure.

I think the records from the A&N CSL are available yet. Do a search and I'm sure some info will appear.
Seems to me a University in Scotland had the records and would search them for a small price and photo copy the page or part of the page that contained your request.