S&W bluing that early would have been by the Charcoal Blue method.
That was done by placing the polished parts right in and then coved with burning charcoal.
Plain charcoal burns all by itself at 830/850F ,,just the right temp to impart the deep blue/black color to steel.
Any hotter and the parts will turn grey color.
900F is about where steel starts to glow red. Getting them that hot ruins any attempt at a blue/black and the parts need to be stripped, re-polished and re-done.
The process was done by all the mfg'rs here and in Europe.
It's simple but labor intensive. Most factories used a lot of child labor for much of it (consider the era).
The parts were usually handled by mearly hanging each on a wire or a hook. The part needed only to be able to be removed quickly and turned/repositioned in the embers and covered again as the process proceded.
Sometimes a stubborn coloring area or part needed to be rubbed or burnished down during the process with such things like a fine abrasive as Rottenstone & Oil (Whale oil) and go back into the coals.
The part was simply pulled, layed down on a wood surface and the deed done and back into the fire.
The wire or hanger may have scratched the crown as the bbl swiveled around on it during the operation and I suspect there was no real attempt to make sure the muzzle was a perfect blued finish with a curved hook wire or rod protruding.
A quick bright polish to the muzzle would take care of that detail and add a nice look as well.
When the color was correct, the parts were again rubbed/burnished down. Sometimes with the above method. Some others simply used oakum(sp?) & oil or burlap & oil.
Depends on the factory and who was doing the work.
The color is nearly the same as the later American Gas Furnace Blue system using Carbona Oil.
But there is a slight difference and side by side you can generally see it if the examples are pristine.
Of course the metal polish under the bluing has much to say about the final look.
The Amercian Gas Furnace system came into play and elliminated all the dangerous hand labor around the open hearth pits and sped up production.
Colt switched to AmerGas Furnace from Charcoal Blueing just after the start of 1911 Pistol production. The very first 1911's were Charcoal Blued.
I'm not sure when S&W switched, but likely around the same time is my guess.
