I have three originals that I shoot. Personally, I want to know about barrel wall thickness. The shiny bores may not be such a good thing, as they would likely come from heavy honing or reboring (the rest of the gun isn't shiny). On the barrel flats there should be a bore stamp (12, 14). You want to measure the bore at the muzzle, and deeper if you can, then compare it to the nominal measurement for the proofed gauge. If they match, or come vary close it probably hasn't been rebored. Ideally, I would want a gunsmith with real knowledge of laminated barrels to run a wall thickness gauge on it.
As to loads, we in the USA have gone to heavier and heavier loads shotguns. This is especially true of Turkey hunters, and for good reason. But, Brits and Europeans (and their guns) were usually intended for lighter loads. 7/8 ounce would be typical of target loads for a 12 gauge, Olympic loads are 24 grams. One ounce or 1 1/16 ounce would be game loads, including pheasant (which is about what I use hunting pheasant, 7/8 for grouse and woodcock). I use 3/4 ounce loads of 8 1/2 shot on targets, usually 68 grains of FFg, but Fg will lower your pressure and likely tighten your patterns. Such loads are probably what the maker of your gun had in mind for it.