hanks Jim for this... great info.
(Just FWIW, one of the steps S&W took was to trademark the color case hardening on their triggers and hammers. If the Spanish did not do that, their guns wouldn't look like S&W's; if they did, the importer could be sued for trademark infringement. And S&W uses that coloring to this day to keep the trademark protection in effect, even though there is no need to case harden MIM parts.)
One of the things I have always liked about my S&W s was the color case hardening.