|Name and Model Number||Hoffman Airplane Designer |
|Country of Origin||USA|
|Date of Manufacture||c. WW I|
|Front Scales||25 various|
|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.
|Donor||Collection of Mike Frey|
(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.|