That one is bulletproof.
The 18.2 tells us it is a 12 gauge. The “Non pour La Balle” marking tells us there is a tight choke in the left tube, and the factory didn’t want you firing pumpkin ball slugs in it. 70 is the length of the chambers, translates to good old 2 3/4” here. It was proofed in St. Etienne in a finished state with French proof powder T. Your gunsmith can measure the bores and chokes for you. The 18.2mm was measured 9” from the breech, is fairly snug for a 12 gauge, and if it doesn’t measure within a few ‘thou of that, now, the bore has been tampered with and the gun is no longer in Proof. Sounds worse than it is, most of the time, most Darne R models have a ton of wall thickness.
The cosmoline thing probably didn’t happen at the factory.
I’d use light loads in it, but, you do you. The gun itself is up to whatever 2 3/4” round you can find. Short of steel shot.
Might want to figure out what is going on with that stock, first, however.
Enjoy.
Best,
Ted
