The front derailleur I had listed on my auctions to Ebay is not late 1950s as thought, but a very similar looking derailleur, and apparantly still somewhat rare, although the word "rare" is used too loosely these days. I've gotten letters by email from a few folks on and off the list who I highly respect, but even their thoughts are conflicting. One party places this deraileur between 1963-65, and a second anywhere between this era and later 60s.
I cancelled the auction and wrote the bidders with the reason for cancelling, and have relisted with an accurate a description that George Allen and I can give, as it is George's derailleur that I'm selling.
If anyone on the list has better information on this derailleur, please email on or offlist. I'd like to know exactly what I'm selling for future reference.