Perhaps a little more information might be in order. Barrel length and condition, proof marks and is it in proof? Current bore diameter, chamber lengths, chokes, LOP....all the usual stuff. Looks like it may be a Jones Underlever. Good pics of the proofs and any aspect of the gun that doesn't seem quite right as well as some close ups on the engraving to judge quality.
Charles Osborn was a well known Birmingham maker. And produced fine enough guns but the value of his name is similar to the vast majority of English makers. Nothing special.
That gun has certainly been refinished, possible even restocked. Barrels are highly likely to be Damascus, but the figure has been covered up by the blue job. Rough guess would be 1890's manufacture. The chambers are probably 2 1/2", if they haven't been lengthened at some point. Jones underlever action, and it looks like the action may have been polished, but it's hard to say for sure without close up pics.
I'm thinking saskbooknut is on the money in the gun assessment but I have a suspicion his valuation may be a bit high. VERY specialized (read 'small") market for a gun like this.
I'll grab more pics and try to get more info tonight.
I haven't measured the bore diameters, but it is a 12g full chokes on both barrels, British nitro proofed, 2 3/4" chambers and good for smokeless powder. If I had to guess, I'd say 30" barrel, but I will check later.
Lockup is rock solid, bores are great, hasn't been refinished or reblued. It is missing one firing pin and has a cracked butt plate.
Also, pardon my ignorance, but what does "in proof" mean?




























