Let’s look at some styles first, or perhaps more appropriately, let’s understand the terms for those styles. There are: the military full-flap holster, Slim Jim, Mexican Loop, Mexican Loop with Cheyenne swell and of course, the Mexican Loop with Texas Jockstrap — seriously. Then there’s the one made famous by Hollywood, the Buscadero rig. Also there are names to link with how one gets the six-shooter out of the holster. There is straight draw, reverse draw and cross draw. Other facets are; safety strap or thong, open end or plugged, lined or unlined. Then there are gun belts, cap pouches, cartridge loops and of course the famous money belt.
Now let’s look at details. The earliest holsters for Colt single action revolvers came from the U.S. Army. When they adopted Colt cap & ball revolvers for their Dragoons (later to become cavalrymen) they were looking for holsters to protect the weapons from the elements. Quick draw as popularized in dime novels and later in cinema was never a factor. Therefore, the army came up with the flap holster. It is simply a leather pouch with a full flap covering the top of the revolver. It keeps the handgun in and (hopefully) the weather out.
As Colt revolvers became standard items of attire in some places, mostly beginning with the California gold rush of the 1850s, civilians began to need holsters too. All that was done initially to make civilian holsters was take the basic military full-flap style and cut the flap off. Because most revolvers at this time had long barrels this gave the holster a long, slender look. Hence they became named Slim Jim.
By the late 1870s and early 1880s another style of holster was in widespread use in the Old West. This one was called the Mexican Loop. It consists of a large single piece of leather cut so the holster pouch itself slips back through one or more slits cut in the black flap. This results in a slot through which the gun belt slides. Mexican Loop holsters can be found with one, two, or even three slits or loops. A rather attractive variation in appearance — if not in name — is the Mexican loop with Texas Jockstrap. In this variation there is another loop going vertically around the end of the holster.
One fault of the Mexican Loop holster design is the leather pouch tends to grab to the revolver when it is drawn. Then the pouch will pull right through the back flap’s slits. This problem led to the Cheyenne swell. That is nothing more than a bulge in the seam of the pouch that sets between two of the back flap’s loops. That little alteration locks the holster pouch tight so the handgun can be drawn. A stitch attaching the holster pouch to the back flap works as well.
Buscadero rigs are those seen in western movies and old TV western programs. They are holster and belt combinations. The belt is contoured so it drops low on the side where the handgun will be worn. Then the belt has a loop through which the holster hangs to drop it even lower: so low in fact the holster needs to be tied to the wearer’s thigh to keep it from swinging all over the place. It’s a most impractical way to actually carry a revolver, more suited to Hollywood “gunfighters” or the quick-draw crowd.