http://www.rockislandauction.com/viewitem/aid/67/lid/1296

Wheel locks are one of the less common types of early firearm ignition systems, as the were much more expensive as the contemporary flintlocks. The wheel lock had a major advantage in reliability, though. Many surviving wheel locks are quite ornate guns, as they were valuable enough to be kept away from much field use and thus preserved. This example is a double-barreled and highly decorated piece with independent locks for each barrel.