# 4 The Slide Rule Collection

The present collection contains a total of 272 slide rules, with 247 linear slide rules, 20 circular rules, as well as 2 and 3 spiral and helical rules, respectively. The “rule” for entrance into the collection is that there must be a logarithmic scale as part of the device. Hence sectors and Gunter’s rules are eligible, for instance, though they are not technically “slide” rules. However, items such as Addiators, Curtas, and other mechanical computational tools are not included.

Looking for a particular rule, or set of slide rules? A Searchable Table can be used for a quick scan of the entire collection.

Top to Bottom: Slide rules with major scales of length 20 (Nestler), 16 (K&E), 11 (Davies), 10 (Pickett), 8 (K&E), 5 (Faber-Castell), and 4 (Hemmi) inches. And a circular Gilson Binary slide rule to round things out.

The following tables provide a short summary of the slide rules. As can be seen, the largest portion of the collection has been produced by a few major manufacturers:

Maker Number in Collection
Keuffel & Esser 72 slide rules
Hemmi 33 slide rules
Pickett 32 slide rules
Dietzgen 18 slide rules
Faber/Faber-Castell 13 slide rules
Lawrence/Engineering Instruments 9 slide rules

As for the rest, the number of slide rules in the collection and their manufacturers are summarized here:

Number per Maker Makers
$$> 6$$ slide rules
6 slide rules Aristo, Charvoz-Roos
5 slide rules Felsenthal, Nestler, Richardson, Sterling
4 slide rules Concise, Gilson, noID
3 slide rules KHH, Kolesch, Relay-Ricoh, Thornton
2 slide rules Acu-Rule, C-Thru, Festus, MARC, Otis King, Rietz, Unique
1 slide rule Alco, American Blueprint, Baetzmann, Blundell Rules Limited, Boykin, Davies, Dennert & Pape, Dring & Fage, E.S.A. London, Factory10, Fearns Calculators, Fowler, Goodyear, HH, J.B. Carroll, Jacob and Halse, Kahl Scientific, MATSKU, Novotni, P.A.S. Co., Reiss, Ruyi, Staedtler, Stanley, UIF Shanghai

See Some Collection Statistics for a few more properties of the distribution of slide rules in the collection.

The sections of this chapter tabulate all of the slide rules in the present collection, organized by slide rule makers and ordered by the presumed manufacturing dates. Chapter sections are in alphabetical order of the major manufacturers where three or more rules have been collected. However, the Other Rules section contains roughly 12% of the total number of slide rules, including many of the more significant items.

A few images of representative rules are given at the beginning of each section. Model numbers in the tables are linked to an image of the slide rule, typically of its front face. More complete sets of images will become available when time allows. For those who would rather just “look at the pictures,” a complete set is provided in The Collection in Photos.

In the tables found in the following sections, production dates for the slide rules are provided. Each date is at least a best guess, though some dates are fairly accurate based upon serial numbers or details of the particular slide rule.

• If the Year of the slide rule is fairly certain, through a serial number, date mark or other documented knowledge about the rule, then there will be a single year listed with no preceding “c.” (circa) in front of the date.
• If the Year is not certain but a narrow range of dates for a particular slide rule can be determined, then this range is provided in the Year column.
• Otherwise, a “c.” will precede the date in the Year column, signifying a guess with a much wider range of uncertainty.

Other information found in the tables includes:

• Typ = type of slide rule: L (linear), C (circular), S (spiral), H (helical)

• Mat = primary material used: wd (wood), bb (bamboo), pl (plastic), ss (stainless), Al (Aluminum), Mg (Magnesium), iv (ivory), pp (paper)

• Size = length of the slide rule’s primary scale (e.g., “C”), in inches (total “path length” if circular, spiral, or helical slide rule)

• Serial = serial number or date stamp found on the slide rule