I appreciate the dating info on those "sleepers" you mentioned. I had read elsewhere, and from quotes of who was there at the time, that Studebaker springs were getting thinner and thinner local, and saw steel also used, then the switch to some manner of 1095. But, will stick with printed book as primary.

Back to that "why" question on the M. I can see doing so if selling both types, so the end user knows which knife for what job...but, if only steel used from then on, it would only serve either the shop folk in knowing what steel was used on a knife later on, or a non-existent at the time collector market in telling them apart.

So, why would shop want to be able to tell newer from older at that time? And keep doing so for year after year. Some manner of tracking, either performance of old knives or new, is my guess, still. If local Studebaker supply held out all the way until 1962, then perhaps to see if new knives held up as long as old?

Thing is, this predates Vic Hangas, by Vic's time Rudy could have simplified any answer to a query to something as curt as, "because I changed steel," and the reasoning behind it lost in mists of time.

Am hoping those with more resources can answer.