So my Simplex SLJ derailer was acting sluggish and not taking up chain slack when I was shifting down to my small chainring. I inspected the upper pivot (where the mech. attaches to the braze-on), and just inserted an allen and attempted to loosen the hanger bolt. A little too much torquing later I heard a snap and realized my mistake. Does anyone know of a source for replacement lipped washers? For clarification there is a great photo on flickr that shoes the part I am talking about.
Thanks to stronglight on Flikr for the image!