Cobium 60 Calculator (ca. early 1960s)

Nuclear Consultants Corp., a small radiopharmaceutical company in St. Louis (taken over by Mallinkrodt in 1966), was best known as the producer of Cobium 60 sources for use in brachytherapy. The idea was that cobalt-60 would serve as a substitute for radium-226, hence the name cobium and the fact that Cobium 60 was calibrated in milligrams of radium-equivalent. An account in E.R.N. Grigg's Trail of the Invisible Light would seem to suggest that Cobium 60 was a metal alloy that might have been developed by Joseph Morton and George Callendine at Ohio State University.

The purpose of this calculator was to assist the physician determine the appropriate treatment time when using Cobium 60. The instructions on the front and back explain its manner of use. 

Since the calculator has a copyright date of 1959, I assume it likely dates from the early 1960s. 

Size: 5 1/4" diameter (cardboard)