Luma Inc., Spinthariscope (ca.1950s, 1960s)
This is an inexpensive black plastic spinthariscope produced by Luma Inc. The company letterhead summarized their business as follows: "Radium luminous compounds and fluorescent zinc sulphides manufactured and applied." Luma Inc. operated a plant at 305 East 46th Street in New York City, and a laboratory at 3532 Forbes St. in Pittsburgh. In the mid 1960s, they seem to have vacated their NYC address and moved to 46-12 34th Street in Long Island City. Around this time, breath samples from the Luma Inc. employees were analyzed by Victor Hess at Fordham University. Quite likely, some of the equipment used were the Hess ion chamber and electrometer.
As expected, radium-226 is used as the alpha source in this spinthariscope.