b61-275 GRAVITY INCLINOMETER. Johnson Pendulum Level. Patented in 1931 by Delbert Johnson of Bloomington, CA. 24" aluminum body with shafting groove and hanging semi-circular indicator. The patent describes the central compartment as being filled with a liquid to magnify the scale and dampen the movement of the indicator, and the handful of other examples we've seen contained a viscous fluid. This one is completely dry with no trace of ever containing any fluid. Marked with the patent number and the words "Pendulum Level." A rare inclinometer in immaculate condition. From the collection of Don Rosebrook. Fine 1000-2000