On a whim, I decided to measure the radiation level of this Tokyo Kogaku (Topcon) lens. It is an unusual lens in that it doesnt have an aperture control ring. There is an aperture mechanism, but if is controlled by the camera (like a Topcon Unirex or Topcon IC-1). It is a sharp lens, but given it was the more affordable line (the RE was 50% more expensive), didn't expect Thorium was used for the lens. Then again, it is a 50mm from the 1960s.
You'll be surprised to know that the relatively common Fujinon 55mm f2.2 in m42 (fujica st) is also radioactive. I know I was, as that has never been identified before, AFAIK. This is without EBC coating, just regular coating. Front shows 13.64 instant, 13.2 avg. Btw, that is not insignificant.
This is a #lens branded Porst, a german photo retailer & mail order company that no longer exists. I’m hoping that someone might have some insight on who might have manufactured this lens. It is a 24mm f3.5: multi coated, with a #Fujica AX mount, for #porst CR1 CR3 CR5 and CR7 cameras, and fuji AX1, AX3, AX5 and STX cameras. Says “lens japan” but not made by Fuji. Fuji had a 24mm 2.8. Porst had a few rebranded fuji like the 50mm 1.2.