Please describe the item in as much detail as possible. Detail does not mean "in good shape" ,describe how the wood is, how much blueing (% of original finish left) there is etc., and anything else you see that may be helpful. Tell us all marking, words, and letters anywhere on the gun...
It isn't a flintlock it's a percussion shotgun. There is no make and model like we have in modern times, these were made one at a time by hand in small shops in cottage industry fashion.
There will be proof marks on the underside of the barrels, you will have to dismount the barrels to find them. These can point to the nation of origin and general time frame and that is about all you might ever know.
Well, first of all it isn't a flintlock. It's a percussion shotgun. As Griz said, there is no model and as for who made it, unless there's a name on the rib or perhaps on the bottom of the barrel set, you probably will never know who made it. It is typical of double guns made from about 1840 into the 1870's. Looks to be in pretty fair condition.
Ahh..we were posting at the same time. If it's European or British yes, it should have proofs on it except for Germany which was not a nation until 1871 and had no proof law until 1891-93.....and I don't believe it's German.
Sharps, going by the looks of it I'd say it's either British or Belgian made and made to resemble a British double gun. And yep, it does look very nice on the outside, If the internals are as nice, it would make a good shooter once the gauge has been determined.
You first need to figure out country of origin, that will affect the value. Then you need to find out if it is functional and still safe to shoot. To look for the proof marks you need to withdraw the ram rod. While you have the ram rod out put it down both bores to make sure it is not still loaded. Sometimes these guns were left loaded just in case the owner needed to shoot that fox raiding the hen house and sometimes they were stored away loaded. Black powder if it stays dry can still be viable even after a couple of centuries in an attic.
Next step place both hammers in half cock, that will be the first of two clicks you will hear when you cock the gun. Next withdraw the key that is in the forearm, sometimes these are captured and will only withdraw just far enough to remove the barrels so if it won't come all the way out don't force it. With the key withdrawn raise the front of the barrels and move them forward, it has what we call a hooked breech, raising the barrels will let you slide them forward.
After you verify that the gun is unloaded you can if you wish test the locks and triggers for function both hammers should make two clicks as you pull them back. in the first click or half cock notch the triggers should not set the locks off and a gentle bump on the back of the hammer should also not set the locks off. with the locks in the full cock notch the hammers should also not go off if the hammers are bumped but the triggers should set off the locks. to prevent damage to the nipple from dry firing it you can put something on the nipples like a plastic valve stem cap off of a tire or even a small leather pad.
If it's English it's worth more than if it's Belgian and if it's fully functional that will add value and if the tubes are not pitted or rusted on the inside, that will add more value.
Also if you clean it up be gentle with it, don't remove any remaining finish on the wood and don't take a wire wheel or sand paper to clean off the outside of the tubes just remove any dust, dirt, congealed oils from it. an overly aggressive cleaning will cut the value in half.
If it's safe to shoot and it's English, I'd guess the retail value would be around 500 to 800 dollars, expect about half of that if you sell it to a dealer. Take away a hundred or so if it's Belgian and if it's a wall hanger, unsafe to fire, you could probably get 2 to 3 hundred ( again about half of that from a dealer ) retail because it's a very nice piece to hang over the mantle piece or on the wall of a man cave.
That will depend on whether or not who actually made it can be ascertained. You need to pull it down and see what's on the bottom of the barrels. If it is Belgian then condition is everything. If it's British the value just went up, again, depending on condition. It should run anywhere from $200-$400 up to maybe $1500. Don't get your hopes up. A $1500 double muzzleloader like that is very rare.