This is the original exposure calculator made by Glernn Le Drew in 1998 of "the Satary Room" in Nepean Ontario, Canada. It has never been outside my observatory and is in new condition. I have gone CCD and digital, so I do not use it any longer. It allows you to calculate the exposure of everything including Sun, Moon, Planets deep sky objects and even comets all indexed to your F ratio and the film's ISO index. It is made of hard plastic and is about six inches in diameter with two rotating indexes. The original book of instructions are included. This device will save you lots of trial and error if you are doing film photography.
$35 including postage in CONUS.