AECL Decay Calculator (1960s)
The Decay Calculator was distributed by Atomic Energy of Canada Limited (AECL) in the mid to late 1960s—it carries the date 9-64. It is identical to the Decay Rate Calculator except that it is made of cardboard rather than plastic.
To use, you line up the half-life of a source with the elapsed time, and the calculator tells you the remaining fraction of the source's original activity. The back of the calculator has a table of half-lives for various radionuclides and a conversion table for units of time.
Size: 5.5" diameter