P.S. I am interested in the Repro-Clarons as part of my study of radioactive lenses. The Repro-Clarons include glass containing thorium and are thus mildly radioactive. They typically will have a slight yellow cast from self-induced radiation damage of the thorium glass.
I have some information about thorium-containing optical glass on my Aero-Ektar webpage at http://home.earthlink.net/~michaelbr...aeroektar.html. I should update this page with info that I have learned since I wrote it. You can remove the tan color cast with UV light.