Full Details

Name and Model Number Cox's Compressed-Air
Discharge Computer
Country of Origin USA
Date of Manufacture Prior to 1928
Front Scales Compressed air discharged, Initial gauge pressure, Length of pipe, Loss of pressure
Back Scales none
Scale Length Varies
Type of Rule Disc
Construction Printed cardboard
Area of Use Technical
Comment Used for calculations related to sizing pipes for compressed air.
Computer bears the imprint "Designed by William Cox", who patented his design for the first duplex slide rule in 1891.
Published by Ingersoll Rand Co., New York.
Rarity RRR
Donor Collection of Mike Frey
Match Number 229
(Click Picture for Details)

In conjunction with our 'donors' we assign a rarity rating to each item, based on the system devised by Herman van Herwijnen
(1929 - 2004), renowned Dutch collector, author, and creator of Herman's Archive, a collection of 5,000 slide rule images on CD.
• RR = Rare - 1 of 25 collectors has one; it may take a year to find an example in the marketplace.
• RRR = Very Rare - only a few known to collectors; may be several years before it comes up for sale.
• RRRR = Extremely Rare - a museum piece; unlikely that an example will come up for sale.