A commercially made holster for most likely a Colt ’51 or ’61 Navy revolver.
Civil War Era Large Frame Revolver Holster, made for what appears to have the outline of either a Colt 1851 Navy, or possibly a ’61 Colt Navy revolvers. The main body is a departure from the typical period holster, using two separate pieces, the flap integral with the back panel. The original plug at the base is firmly in place. Gussets are use between the two panels allowing for more internal space, and help form wide welts along both edges. Embossed line in the leather highlights the shape of the intended revolver.
The belt loop on the back, even with allowing shrinkage, I doubt it would have fit onto an military waist belt of the period, with only a civilian rig usable (2 inches max). The stitching has popped along one side and some of the bottom of the belt loop. Stitching elsewhere is strong. The flap stud is a gutta percha (hard rubber) button, secured to the body with a wire and it appears to be the original.
Leather shows some areas have a crackled finish where the leather is use more often, especially on the top section of the flap, and around the stud slot. Still, a great looking holster, and ideal for the western collector.