Originally Posted by
wrk101
Go with a claw type derailleur and just about anything will work. Otherwise, you will need a Simplex derailleur, which show up pretty often on ebay. You lost me at non-threaded dropout.
I should have said derailleur hanger. On my PX-10 the hanger is not threaded, thus a more modern derailleur with the bolt tightening from the front of the derailleur will not thread into the hanger. The Simplex fits into the hanger and then a bolt is inserted in the back of the hanger into the derailleur to attach it to the frame.
I didn't know about the different washers so I'm glad I asked.