It's some kind of Arabic or Indian firearm. Possibly a miquelet action. Predecessor of the flintlock. The Arabs used miquelet muzzle loaders well into the 20th Century.
I suspect it's missing some parts and has had some bits added too.
There are some good pictures of the action here. Your's isn't worth the same kind of money though.
http://www.collectiblefirearms.com/R...Flintlock.html