Not at all. Many USA-Schrades were stainless. And the knives with the "SCHRADE +" tang stamps are always (Ugh, I hate to say that) stainless.
Bob, you make a valid point about using the terms "never" and "always" in conjunction with Schrade knives.
Generally, SCHRADE+ is almost always stainless steel. Uncle Henry knives are
usually stainless and Old Timers are
usually carbon steel. There are notable exceptions to all of these. Early in production, the Uncle Henry 153UH
Golden Spike was carbon steel. Later it was changed to stainless. The LB-7 Bear Paw Lockback was stainless from the beginning. I have one simply stamped SCHRADE (no "+") although it is also stainless. The 152OT
Sharpfinger (and most of the OT line as well) was carbon steel from the introduction in the early/mid 1970's until about the late 1990's when they were made from stainless (not marked with the "+").
As Kieth noted, spotting and the beginnings of patina are the surest indicators that Schrades are 1095HC carbon steel and not 440A or 420hc stainless. On the fixed blades, the exposed tang (or the choil where handling marks are seldom cleaned off) is usually the first place spotting is seen.
Note also that "in the latter days", Schrade used some more exotic modern steel on a few knives.
Codger