Howdy
The drop loop holsters made famous in Hollywood were often called Buscadero rigs. Absolutely not good for riding a horse, they would flap around like crazy. Also not so good for sitting in a chair, very uncomfortable. About the only thing they are good for is fast draw in the movies. Buscadero rigs would not have been worn in the Old West.
http://www.alfonsosgunleather.com/Pages/western2.htm
Large frame S&W revolvers were not common on the frontier. S&W did not make any large frame 44 or 45 caliber revolvers until 1870. Prior to that everything made by S&W were little Tip Up 22 or 32 caliber revolvers like these. They were designed to be slipped into a pocket, not worn in a holster. There were many thousands or these made. The large one is a Model 1 1/2, 2nd Issue made in 1873 and chambered for 32 Rimfire. There were over 100,000 of this model made. The little is a Model No. 1, 3rd Issue made in 1870 and chambered for what we would call today 22 Short. There were over 131,000 of this model made. There were also several other Tip Up models made, they were produced in great numbers, and they found their way into pockets everywhere, both East and West.
S&W produced their first large frame revolver in 1870. The Rollin White patent, which Smith controlled was about to expire. The White patent made it illegal for anybody else to produce a revolver with chambers bored out for cartridges. So when the White patent was about to expire, and everybody and their brother was about to enter the cartridge revolver market, S&W unveiled a radically different revolver, a large frame, Top Break, 44 caliber revolver. The barrel was latched at the top, hence the name Top Break. The barrel pivoted down for loading and all empty cartridges were automatically ejected. It fired a round that later came to be known as the 44 S&W American round and the model eventually became known as the American model. There were slightly more than 28,000 Americans produced, so they were nowhere near as popular as the little Tip Ups had been. The Russian Model, produced from 1871 until 1878 were produced in great numbers, over 150,000 were made, but as has been stated, most of them were sold to foreign governments. The Schofield Model was produced from 1875 until 1877. The first 3035 were produced on contract for the Army. There were 5964 of the 2nd Model produced. By 1878 the Army had surplussed them all out, but there were never very many made in the first place, so they would not have been common in the Old West either.
These models were followed by the New Model Number Three and the 44 Double Action. All shared the basic #3 frame size. Remember, all Schofields are #3s, but not all #3s are Schofields. Here is a web page that describes the five different models that were built on the #3 size frame, and how to tell them apart.
http://www.armchairgunshow.com/Mod3-info.html
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Smith and Wesson did not start producing Top Break pocket pistols until 1876, starting with a 38 caliber, 5 shot, spur trigger model. This 38 Single Action, 2nd Model, five shot, Top Break pocket pistol was made in 1877. There were over 108,000 of them made.
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At the end of the Civil War there were many thousand Cap & Ball revolvers that the Army surplussed out. They were very cheap and many adventurers heading for the Old West bought them. Colt did offer conversion models of their C&B revolvers, but never made very many. They did not bring out the SAA until 1873, three years after the White patent had expired. So until 1872 or so, if somebody wanted a large frame revolver, it was probably going to be a surplus 44 or 36 caliber C&B. Even after 1873, the SAA was very pricy, going for about $12. A dollar a day was considered good pay for a cowboy in those days.
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Back to holsters. Most holsters available at the time were 'high riding' holsters. Not the silly drop loop Hollywood holsters. I'm no horseman, but I don't think a short barreled high riding holster would be much of a problem for mounted man.
I had this rig made up when I first started shooting Cowboy about ten years ago. It is a high riding rig in the Duke style. Not authentic to the Old West, the Duke style was first made for John Wayne by Tom Threepersons in the 1930s. But it is a high riding rig similar to many that were being made at the tail end of the 19th Century. Of course no real cowboy would have been able to get his hands on enough money to own two pistols.
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Regarding open carry in the Old West, the Shootout at the OK Corral in Tombstone in 1881 was a direct result of the city ordinance forbidding the carrying of weapons in town. Firearms were supposed to be surrendered upon coming to town. Marshal Virgil Earp decided to enforce the ordinance when he found out that the McLaurys and the Clantons were packing and they were being belligerent. Being townsmen, the Earps did not carry their pistols in holsters, they typically carried them in the waistband of their trousers. Holiday had a pistol in a holster but it was hidden by his coat. Wyatt testified at the trial that he was carrying his pistol in his coat pocket.