This rectangular aluminum instrument has a scale of reciprocal inches, unevenly divided and labeled R I; a scale of equal parts, labeled I and numbered by ones from 1 to 10 and by tens from 15 to 95; ...

I first became familiar with the Gerber Scale while recently speaking to a couple of NASA retirees who worked on the Apollo program back in the 60s. They are Ray Melton, who was in the Lunar Module ...