I recently purchased a cased tintype of an armed soldier. The soldier is wearing a pith helmet, a jacket that looks like something out of a Wild West show, a belt buckle that says US on it, the trousers appear to have a Marine Corps blood stripe down the leg, and is armed with what appears to be a percussion cap rifle with bayonet. I'm going to assume this is post-civil-war. Whatever it is, it's highly confusing.

Any help identifying the unit and the time frame would be greatly appreciated.