Up for sale is a tiny piece of history in the form of an original, antique brass-trapped John. A. Roebling's Sons wire rope rule. Brass "head" slides out for ease of measurement. Includes a chart for determining rope tensile strength by diameter in inches, weight in pounds per foot, breaking strength in tons of 2000 pounds iron, breaking load in tons of 2000 lbs cast steel for standard hoising wire rope. Opposite side has diameters, min size of drum and sheave in feet and reads "John A. Roebling's Sons Co. Mfr's of wire rope Trenton N.J." This company was famous for its suspension bridges, including the Brooklyn Bridge. This rule represents a valuable artifact of the era.

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