NOT trying to gainsay the official issue equipment. But, there was a LOT of field modifications, or custom equipment created by company saddlers or harness makers near posts. If you can get ahold of "U.S. Holsters and Pistol Cartridge Boxes" by Edward Scott Meadows, there are a bunch of holsters shown both regulation and non, as well as designs submitted for consideration by various officers. Some were manufactured in limited quantities for field trials; some were rejected outright by the Ordnance Dept. Some, like the Miller-Fechet were adopted by the company commander (Capt. Fechet, 8th Cav.), and his superiors looked the other way! The so-called "Ropes" pattern holster was a butt-rear, full flap holster intended to be used on wider belts, although the fact that Ropes himself didn't like the idea of a flap at all makes the naming suspect. The holster shown appears to be a Forsythe style. Regardless, it is one practical style that could be utilized. I do NOT add the cartridge loops around the top of the holster body, as I am concerned one could accidentally hit the primer while holstering the gun. That is also the reason I don't put the loops on the Miller-Fechet holsters.
BTW, I presume you are looking for a holster to fit a Colt's SAA? Would that be with the 7-1/2" barrel or the 5-1/2"?