The C-14 slide rule was distributed by the Nuclear Chicago Corporation, probably in the early 1960s given the copyright date of 1959.
The slide rule had several functions. First, and most important, it indicated the product code and price for a wide variety of C-14 labeled compounds. Second, for a specified count rate and dead time, it indicated the percent of the counts that would be lost. Finally, it indicated the % error due to counting statistics for a specified count rate and count time.