Original U.S. Model 1866 Rifle Musket Three-Bladed Combination Tool. This tool is very uncommon, especially in un-damaged condition. These tools are hard to find because only 25,000 of the M1866 were produced. Also, more often than not, the two tines are broken.
This particular piece is complete and undamaged. To read more about this type of tool please reference Gun Tools: Their History and Identification.