Full Details

Name and Model Number Hoffman Airplane Designer
No. 458
Country of Origin USA
Date of Manufacture c. WW I
Front Scales 25 various
Back Scales none
Scale Length Varies
Type of Rule Disc
Construction Printed cardboard, celluloid indicator
Area of Use Aviation
Comment For calculations related to the design of biplane aircraft, No. 458, price $3.50.
Appears to be for military biplanes; includes information for machine gun, ammunition, and gun turret weights.
Will calculate 33 different components of airplane construction and performance.
Rarity RRRR
Donor Collection of Mike Frey
Match Number 231
(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.