Might be worth carefully steel-wooling those slops of paint to see what they were covering up.

I wonder what would have caused all those bumps and dents on the inside of the lid? The scope was the highest point above the receiver...

These were on issue as late as 1944 IIRC. Tom Barker who wrote about his experiences on Crete as an ad hoc sniper was issued one of these Alex Martin rifles on his way there.