A bit late....

Sorry, I just noticed this post...

If that's an "S" in a square, it's a Savage manufacturing mark.

See our MKLicon entry 1943 No.4 Mk1* Enfield Rifle (Mfg under Lend Lease Act by Savage in 1943)

I'll have to do some research to see what I can fins on CAS....

Regards,
Badger