An update to this thread. I fell down a youtube rabbithole and found a guy who is documenting craftsman ratchets for a book. He said both the "Stainless" and "Lifetime" ratchets were stainless steel, just a slightly different mix of metallurgy. (He tested them) BTW, I have been using my 43765 3/8" Lifetime ratchet for over 35 years now, having bought it in the late 1980's Great ratchet that fits in places a thick-headed ratchet won't go. I finally picked up the matching Lifetime 1/4" 43764 and 43766 1/2" units this month on ebay. So happy I finally have a full set to play with. In case you were wondering, the "Stainless" stamped ratchets were number 43761 for the 1/4, 43762 for the 3/8, and 43763 for the 1/2 ratchet.
Here's that video in case anyone is interested: