Figure 1-3 : A plate from the 20s, 30s, 40s.
I love to use old (vintage) camera lenses for my photography, but tend to stay away from the oldest ones. Up through the sixties, and (for some lens companies) – into the seventies and beyond – lenses were sometimes made with radioactive glass. When this glass was marketed, the term “rare earths” was sometimes used to imply a glass additive or lens coating that contained thorium.
A Storm Of Photons 