Looks like a nice little hunting gun! I love hunting with a SxS. Straight grip, rounded action, easy to carry in the hand and also easy to carry open over the shoulder! With a .012" choke constriction....nearly modified, use spreaders for short range early grouse, soft shot later when the leaves are down.
It is a 2-3/4" (70mm) chambered gun based on the barrel flat marking. I believe it is proofed to 850 bar, which is 12,300 psi. By comparison my wife's 20 year old AYA #2 20 ga is proofed to 1,370 bar, or 19,800 psi. If I am reading these proof marks correctly, I'd want to use modest pressure loads in the gun, ie 1200 fps 7/8 oz loads and 1160 fps 1 oz loads, vs some of the very fast premium "pheasant" ammo available.