actually 531 is older than the '30s, just didn't see use in bicycle frames until (about) 1928 or so. There certainly were frames made from chromium-molybdenum steel well before "the eighties", plenty of Columbus frames from the '60s (maybe earlier, too) were made of it, certainly some early Schwinns, too .
But it's an interesting trivia question: when was the first use of chrome-moly steel in a bike frame that can be documented.