H. J. Gray Spinthariscope (ca. 1920s-1940s)
This can only be considered a "spinthariscope" in the loosest sense. It is simply a radioluminescent mix of radium and zinc sulfide deposited on a glass microscope slide. When viewed under magnification in the dark, tiny flashes of light (scintillations) would be observed as the alpha particles from radium and its decay products (primarily nuclides of polonium) deposited energy in the zinc sulfide crystals.
This particular example was probably produced in the UK. The handwritten text on the label (written by H. J. Gray him/her self?) appears to read: 2" objective or pocket lens.
Microscope slide spinthariscopes similar to this one were very common and often sold by scientific supply companies.
Size: 1" x 3"
Donated by the Health Physics Society.