Caltex grapholex

Nomogram) Made in France for Calcrude, a division of Chevron Oil Company Front Scale (Extended Scales) 17cm // B3(K), B2(A) [ b2(B), a(CI), b(C) ] B(D), L Back: Nomograph for determining viscosity of oil at varying temperatures. Cursor: unusual lens with diagonal hairline to use on back side nomograph. Well: Farenheight to Celsius conversion. Note 1: The American Petroleum Institute gravity, or API gravity, is a measure of how heavy or light a petroleum liquid is compared to water: if its API gravity is greater than 10, it is lighter and floats on water; if less than 10, it is heavier and sinks. Note2: the cursor is removable to place on the back side to calculate the viscosities on the nomogram. it's in perfect condition. I. original case.