I was eyeballing a 1951 Italian frame a while back. Not expensive, about $200 shipped to my door. Had the 4mm adjustment screws and the cable stop at 4 oclock. This was specific to the first gen GS. Cool frame but I would have to buy a $2000-$3000 derailleur to make it work. I passed. Neat frame though.
Wish I had thought about this potential trap before I started. No I don't have a suicide front derailleur in my spares box either! $$
After looking at my other simplex 50's derailleur hangers which are not threaded like this - I am coming to the conclusion that the dropout has been modified to accept campagnolo threading and hangers. Cut and threaded.
Going to take my time but I think putting the simplex tour de france derailleur on here whether the hanger likes it or not. any objections? Its a repainted repaint frame anyway.
http://imgur.com/xMTl2sn
http://imgur.com/bE7XQKk
edit - normally I work on 70s and 80's bikes so I am learning as I go here