Anyone up on proof marks, these on on an old FN Mauser

Top is the receiver bottom is on the barrel

You need a gun digest or blue book that might help with that.

A quick Google search for "Belgian proof marks" gives you everything you need.

You know I must be getting old I didn’t even think to google it

I'm somewhat familiar with shotgun proofmarks and I assume rifle proofmarks would address similar areas of concern. Proofmarks will tell you if the gun was proofed with smokeless or black powder, chamber length, gauge/caliber, choke, etc..

As coonlove mentioned, Google "Belgian Proof Marks" and you'll find a list of tables that will match the proof marks from whatever era the gun was manufactured. It can be an interesting study.