Derailleurs are older than that, the 30s is when you start to see production models. Try these sources:
Dancing Chain and
Data Book. Both are supposed to be incredible, both are strangely out of print. I've paged through the
Data Book and what I remember was very good.
Vintage Bicycle Quarterlyhttp://www.mindspring.com/~heine/bik...ite/index.html.
Awesome scholarly journal! A little OT but mandatory nonetheless.
Tony Hadland:
http://www.users.globalnet.co.uk/~hadland/
Rob van der Plas publishing:
http://www.cyclepublishing.com/
I'm forgetting lots of others but these are all good.