They're most likely picked from old hardware. I got two 060/50 from a friend a number of years ago that he rescued from discarded cards from some industrial robots. They just switched the cards when something went bad and threw the old one away.
These are probably scavenged in a similar way by someone who knew there is a market for them.
Never had the opportunity to test if those CPU's I've got are ok or not since I have to rebuild my CS MK-II to do that and if they don't work I'll have to convert it back again...
