Colt Special Contract Musket Model of 1861, It's based on the Enfield Musket. It actually should be a three band musket, but your center band is missing.
Value.... Hard to say from that pic, we'd need a good shot of the lock, and the finish on the metal. Prices are all over, from a couple hundred in rough shape to a couple thousand in like new condition with the metal still in the white....
You may already know this, but some people don't.... Those old rifles cannot be fired with modern Pyrodex, they are made for real black powder only. Loading anything other than black powder in them you can destroy the gun at best, and seriously injure yourself at worst.... Even so, we're talking about a gun that is 153 years old. I would want to run a bore scope down that barrel and look for any pitting or active corrosion. My advice to people is always this.... If you have an old gun like this, and you want to shoot it, don't.... If you're not well versed in firearms take it to a good gunsmith and have it thoroughly checked out for safety first.
If you do shoot it I would definitely suggest using a lighter load, I just wouldn't want to chance having it damaged if it were mine....
