Actually, it belongs to my wife's cousin. The only markings are the name on the side plates - POWELL. The muzzles measure about .728, and by the dimensions of the outside, there appears to be very little choke.
Anybody know anything about this gun?

IM jaybe

Here's another picture.
jaybe

looks to be a percussion shotgun....looks pretty old too.......sorry cant help much.....think it would end up being a 12ga smoothbore......never heard of that maker...is thata double gun and i just cant see the far hammer and barrel? or a single barrel?? if its a single it would be left handed.......and id imagine worth a good bit more because i dont think many sidelocks were made left handed..i know not all to many are left handed today......back then i bet it was a rarity....though i may be way wrong......someone here should/might know more.....it looks to be in pretty danged good shape as well.....id hang on to it till you find out more....dont be messin with it or anything that might decrease value till then.....i know money isnt everything....but why take out a 1 of a kind rifle out and shoot it thats worth 6 figures? never know.....

Its a double barrel 12 gauge percussion...the locks were made by Powell...
Makes didn't put their name on the locks...the lock maker did...

Sorry, I didn't notice that the picture doesn't show - it's a double, like nchawkeye said.
It's actually in kind of rough shape. Lots of rust pitting on the barrels, all the blueing is gone. The owner is planning on browning it. For those who are in the know about antiques, is this a good idea?

Thanks,
jaybe

jaybe
Do not and I repeat do not refinnish the gun !! By refinnishing it ,you can devalue it a great deal. Also do not refinnish the wood.
You should find some small proof marks on the barrel neer the breach ,possibly on the under side. These will help you identify what you have there. There is also a book out that values old BP guns , but I don't recall the name. It may be one of the GUN TRADER books.