The salt water "temper" was stainless? I knew about that S but thanks for info on the other, new to me. Still leaves me wondering why whoever would want to know whatever, aside from filling orders. But it went on and on, when only steel in town. Stamping every knife with a separate M extra operation makes no sense when only steel offered, especially right after others discontinued, as for "it's a tradition" argument.

The Studebaker springs were and are popular for forging purposes. I wonder if anyone ever ran an analysis on them, or traced to maker for alloy. And, wonder what is closest, today. My guess would be 80CrV2, aka 1085 Improved, aka 5160 Improved, some cro-moly-vanadium spring steel for heavier purposes.

PS- this all assumes a separate M stamp, every bit of it. If he had an old stamp where he added separate S and T, and also bought a new stamp circa 1962 with added M, then the plain answer is, "because it's the new stamp, and the old one about slap wore out," too simple, Private, long after differences in filling orders needed to be noted. It is what it is.

Pappy, or anyone else, who owns several M stamp blades, a comparison between them would give an answer right quick. I only have the old Smokejumper. If all the Ms are in precisely same place, as in part of one name/temper stamp, then they kept stamping M for that easy reason. It was what they had.