In the beginning, there was the Model of 1900, designed to accommodate a more powerful .38 cartridge, the .38 S&W Special. That soon morphed into the Model of 1905. It went through several modifications, including heat-treating the cylinder, to become the Model 1905, 4th Change, otherwise known as the M&P. That gun went through a number of changes over the years and, soon after the Korean Unpleasantness, was designated as the Model 10. More changes along way ensued, but the Model 10 remained and you can still buy one today.
However, the ammunition used in the 1920s, lead round-nosed bullets, couldn’t punch through a car’s door. They didn’t know about computers and such back then, only slide rules. They couldn’t run designs through simulators, so the only way to make a car stand up to the shitty roads that existed at the time was to make them heavy.
Hence, the .38-44 round was developed. This was a hotter load, but it would beat the hell out of a standard .38 revolver, and, not to mention, the recoil was not fun. So the .38/44 revolver, also known as the Heavy Duty, came along in 1930. This was, essentially, a .38 on the frame of a .44 Special revolver.
But more power was desired. To prevent morons from shooting a much more powerful cartridge, the .38 Special cartridge was lengthened a bit and, in 1935, the .357 Magnum was introduced. A more elegant version of the .38/44 revolver was introduced in “Registered Magnum” and non-registered versions. Both were finely finished and expensive. Gunsmiths began boring out the chambers of .38/44 revolvers. Smith & Wesson responded by bringing out the Highway Patrolman, which was not as finely finished, but functioned just as well and was a lot less expensive.
But those guns were also heavy and cops who spent their careers carrying guns that were never fired, other than to kill injured deer or on a qualification range, wanted something lighter.
To be continued.