Aluminum Ring Badge (1950s)
Unfortunately, I have no background information about the origins of this aluminum ring badge. However, it is so similar to the plastic ORNL ring badge (also in the collection) that I would guess that it came from ORNL. It contains a single small circular disk of film and a circular filter (cadmium?) with a hole in the center is used to compensate for the film's over-response to low energy photons. The hole provided the film with some response to the very lowest energy photons that would otherwise be completely stopped by the filter.