Epson states that it will not work on the RD-1; and Stephen Gandy states that it will not work on the R2.
http://www.cameraquest.com/voigtBR2.htm
Go with the type I regis Summicron. It has the identical optical formula and it will work. The Dual-Range simply extends the focus helical, but it did not change the optical prescription at all.
Anyone who sold a Summicron for $10 does not deserve to own any camera equipment.