Smith put out an M57 is .41 Special in 1964 and again in the 1980's too. Factory ammo was apparently loaded in .41 Mag cases.
No, they did not. S&W has NEVER produced a gun factory chambered for the ".41 Special".
The .41 Special is a wildcat. It was talked about and some experiments along those lines were done decades before the invention of the .41 Magnum, but nothing in the way of a production gun or ammo ever came about. Various notable gun writers advocated such a class of cartridge, believing it would be superior for police work.
Don't confuse a ".41Spl" LEVEL load .41 Magnum with an actual .41 Special cartridge. Unlike the .357 Magnum and later .44 Magnum, there was NO .41Special case to develop the .41 Magnum from.
When Remington introduced the .41 Magnum the plan was to produce two distinct levels of loadings. The Magnum with a 210gr JSP/JHP bullet at 1400+fps and a "police load" with a 210gr LSWC at 950-1050fps (depending on which source you use for velocity).
Remington's screw up (in 20/20 hindsight) was to focus first on the magnum load, producing the police load only in very small amounts in the early years.
This lead to a situation where nearly all police agencies testing the S&W guns used magnum ammo (it was all they could get) and the combination of an N frame gun (which the police weren't really happy with) and only magnum ammo resulted in a combination deemed unsuitable for police use.
By the time quantities of the police load were available the police (as a group) had given the .41 Mag the thumbs down.
Note that what the old time writers wanted (their ".41 Special") is the same load class as today's .40S&W. Remington could have given them that (in the .41 mag case) but chose instead to give them the magnum level first, and that was just too much for police use.
They COULD make an actual .41 Special today, just adopt what the wildcatter's did/are doing but there is no market demand, or niche to fill, anymore.
You CAN get a .41 Special revolver today, but it is a custom thing. And so is the ammo.