As support for the proposition that the Model 58 referred to in the original post is a result of gun smithing; I noticed on gunsamerica that there is a
S&W model 58 in 45 LC with 6 in barrel, (with model 25 barrel and cylinder), with Millett adj. rear sight.
NRA Life Member - Orange Gunsite Member - NRA Certified Pistol Instructor
"When plunder becomes a way of life for a group of men living together in society,
they create for themselves in the course of time a legal system that authorizes it and a moral code that justifies it." Frederic Bastiat