low pressure gas flow computer von fox (1 Ergebnisse)

Zustand: Acceptable. Black fabric covered boards with flap, in good condition. Two specialty rules for determining cubic feet of gas per hour, and other calculations. No date found. Possibly 1936? Previous owner's name on last page. The paper is slightly darkened with age and soiled. There is a crease along one corner of main page. The circular dials are intact and useable. Folder is 6" by 4 1/2". A rare find for collectors of slide and specialty rules. "These Computers are designed by means of Dr. Pole's formula, with ranges best adapted for the use of the Service, Fitting, and Appliance Departments, and issued in a pocket size, convenient for use on the district.".