The crown over the Scrolled BP on the barrels is provisional proof, the crown over block BP on the flats is the Black Powder Definitive Proof. The 13/1 shows at proof it would accept a .719" plug gage to a depth of 9" from the breech but not a .729" gage (12). The 12/C means it has a 12ga chamber of up to 3" length. Chambers longer than 3" are marked LC for long chamber. There is a bit of ambiguity as to proper marking for a 3" chamber as to whether or not it is to carry the LC mark. 3" chambers have been identified with both C & LC marks.
