Spinthariscope of Unknown Manufacture (ca.1950s)
This is a nicely built black metal spinthariscope. The manufacturer is unknown, and there are no markings on it of any kind. The alpha source, radium-226, is incorporated into the zinc sulfide screen. Focusing is accomplished by turning the threaded knob that holds the source-screen. In other words, to adjust the focus we move the screen up and down rather than the lens as is usually the case.