First off- I am no expert. That said, it's my understanding if the tang stamp says only 'Schrade', then it's carbon steel. If tang stamp says 'Schrade +', it's stainless.
There is a lot of confusion about this issue.
First of all, the SCHRADE+ stamp DOES mean that the blade is stainless.
However the absence of the + sign DOES NOT mean the steel is carbon steel.
At some point in time, Schrade began marking their stainless steel blades with the + sign to let customers know that the blade is stainless.
I don't know the exact point in time when they introduced the + sign but based on what the research I have done so far, I suspect the + sign was introduced in the early 1980s, give or take a few years.
Prior to the introduction of the + sign there was no indicator in the tang stamp as to the composition of the steel. Therefore older stainless steel knives will have the same markings as the carbon steel blades.
I hope this helps to clarify the issue a bit.
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