This very unusual Austrian single shot percussion pistol was rebuilt in Belgium and then appears to have been exported to the US. The lock markings are somewhat mystifying as the typical Austrian 852 (1852) is found at the bottom center along with US slightly forward and below the bolster and a US style 1851 horizontally at the tail. This pistol started life as a Model 1851 Austrian Augustin tube lock percussion pistol. The overall length is approx. 16"". The 8 7/8"" round 67 caliber smooth bore barrel has a fair bore with light roughness. It has the oval Belgian ELG proof at the top rear, added when it was altered with the bolster for percussion caps. The barrel tang appears to have numbers but they are indistinct. All metal has a smooth light brown patina. The brass ramrod thimble, trigger guard, and butt cap are very good with a nice aged patina. The ramrod is not present. The shortened stock is fair with a missing chip at the left front at the barrel and a 1.75"" by .25"" triangular chip at the left barrel-tang intersection. The butt cap has a top and bottom screw with a third open hole centered between them which was for the swivel and ring. The action functions correctly. The lock markings of US and 1851 appear to be from the period and genuine to us and another well-known Civil War expert. However, we don't know their origin or what they signify. This interesting pistol certainly merits further research.