| 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 480”s) |
| 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 |
| Thumbnail (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. |