http://www.rockislandauction.com/viewitem/aid/1025/lid/4089

The Palmer was the first bolt action firearm adopted by the US military - it was a single shot rimfire carbine patented in 1863 and sold to the US cavalry in 1865. The guns were ordered during the Civil War, but were not delivered until just after the end of fighting, and thus never saw actual combat service. The design is very reminiscent of the later Ward-Burton rifle, using the same style of interrupted-thread locking lugs. The Palmer, however, has a separate hammer which must be cocked independently of the bolt operation.