Full Details

Name and Model Number Harrow Mark Reducer by
Aston and Mander, London
Country of Origin England
Date of Manufacture ca. 1915
Front Scales C, D
Back Scales none
Scale Length 38" (96.5 cm)
Type of Rule Slide Rule
Construction Boxwood
Area of Use Other
Comment Proportionality calculator for grading quizzes and tests.
Made by Aston & Mander, 25 Old Compton St., London.
Rarity RR-RRR
Donor Collection of Louis J. Gotlib, USA
Match Number 8
(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.