jOe positively IDs the gun as a Webley and it turns out he's full of poop. Hmm. Imagine that.
Myself, I'd not put any stock in the name on a boxlock, but, would put a bit on what it could do for me. Honest English fowlers and pigeon guns are not an easy commodity to price, stateside, boxlock or otherwise.
I still say it would sell for more than an lightly configured game gun.

Best,
Ted