It turns out that the seller of these keys is a member of the Imperial Yahoo Group. I came across his name tonight when reading some emails about trying to install seat belts in pre-'61 cars with swivel front seats. Another member had high praise for Joe Jesser, the seller of these keys, relating back to some work that had been done a while back.
These keys are NOS from key manufacturers. The story on his website is interesting (but bad website):
http://www.jessersclassickeys.com/index.html So if anyone is looking for classic keys, it appears that Joe Jesser is a Mopar guy.