Terry & Doublegunhq,

in the diamond there's 12 over C and at the underside of the back end of the barrels it says 12 over "BC" not 30 as it looked in that blurry photo I sent.

BC may then suggest for example 'brass case' but are there any other possible explanations?

The owner hadn't tried to chamber brass shells nor regulars yet.

Regards,
Saku