Came across this old British muzzle loading shotgun the other day, No makers marks but there are some proofs on the barrels and inside of the locks. The proof on the barrels are Birmingham proof marks but I have no idea what the mark on the locks mean. There is either no makers markings or they have warn off and to top it off someone in the past has done a piss poor attempt at refinishing the barrels. I mean it just looks, excuse my language, shit. Here are some images:

https://imgur.com/a/fkcvIMa

Anyone have an idea of age (My guess would be 1840s?) and what that marking on the inside of the locks means?

Cheers