I've been going to the North Carolina Flea Market for many years, and have found some nice things, like a green handled M7 bayonet for $20 (missing the pommel but an easy fix). Lately it's been kind of dry, the past couple of years haven't really been productive. But, if you collect you must search, and occasionally something unexpected crops up.
Today I was looking a several tables with all sorts of old, rusty tools and "restoration" (read rusty) parts for doors, furniture and the like. I then saw this rusty piece of metal which I recognized as an M3/4/5/6/7 blade.