Smith Carbines made by American Machine Works , Massachusetts Arms Company, and American Arms Company from 1861 to 1865 making over 30,000 total carbines. They are .50 cal. single shot, percussion breechloaders with a sling bar and ring on left side (There are some exceptions in placement but yours looks to be the standard ). There were a very few non military sales your was however a union military issue based on the government cartouches on the stock. I know of their issue to the 7th. and 11th. Ill. cavalry, the 7th. and 17th. Pen. cavalry, and the 6th. and 9th. Ohio. There are more but these are just the ones I am aware of. Value is hard to say, it depends greatly on where you are as to regional fluctuations. Based on you pictures around here $1500 to $2500 would be my guess.