Full Details

Name and Model Number Fowler - - - Mackay
Paper & Board Calculator
Country of Origin England
Date of Manufacture unknown
Front Scales Fixed Outer Scale (Oz per Sheet); Moveable Middle Scale (Sheets per CWT); Moveable Inner Scale (Lb per Ream 480s)
Back Scales none
Scale Length Short scale ~ 10 (25 cm)
Type of Rule Watch Type
Construction Metal with paper scales , glass window, plastic back
Area of Use Other
Comment Single sided pocket watch calculator with two stems to rotate inner paper scales and celluloid cursor.
Outer paper scale fixed.
Made special for F. Mackay & Co. All three scales are logarithmic short scales calibrated for different measures.
Blankenhorn and De Cesaris Model 4MMP1.
Rarity RR
Donor Collection of Dr. Paul J. Tarantolo Jr.
Match Number 21
(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.