My Slide Rule Collection

Keuffel & Esser Slide Rules

My Grandfather's K&E 4088-3 10" Duplex

This slide rule has the improved metal-framed cursor, engraved "Patent Pending", which places the date of manufacture between 1934, when the improved cursor was introduced, and 1937, when the patent was awarded. The serial number, 532933, dates this rule to 1935

In 1935, my grandfather was 24 years old, and worked for Carborundum in Niagara Falls, NY. I don't know if he used this slide rule in his work, but I assume he did as slide rules weren't cheap, and not the kind of thing you'd buy just for fun - it would have cost him $9.35 - a whopping $120 in Y2K money! ( Yes, I did the conversion on my slide rule - but not this one.)

Keuffel & Esser 4054 "Favorite" 10" Mannheim

This is probably the oldest slide rule I own. The lack of a serial number, the frameless cursor, and the serif fonts date this slide rule to 1917-1921. The 1921 K&E catalog describes this slide rule:

The Favorite Slide Rules are of the same pattern as No. N4041, but they are not adjustable. They are an improvement over the imported rules, being made of materials seasoned here and, therefore, less liable to warp or shrink.

An interesting variation on the "Buy American" theme. There is no price in the 1921 catalog, but the 1925 catalog lists this slide rule for $4 ($40 in Y2K dollars).

Keuffel & Esser 4088-3 10" Duplex

This slide rule may be even older, but I can't be sure. The lack of a serial number and the serif fonts date it to pre-1923, but the "improved" cursor seems to date to much later, after 1937 - since it doesn't bear any engraving at all, it may even be as late as 1960 - so I believe it is a replacement cursor. This is the same model as my Grandfather's slide rule, but this rule is especially interesting because someone has very laboriously added an extra scale at the bottom!

Keuffel & Esser N4053-2 8" Mannheim

I've dated this slide rule to 1930. It and its case are in exceptional condition. I also got a book with this slide rule, "The Polyphase Slide Rule" by William E. Breckenridge, published by Keuffel & Esser, ©1925. The slide rule case is labeled "R. Frazee" and the book cover is labeled "Roy Frazee Jr."

Keuffel & Esser 4092-3 10" Duplex

I've dated this slide rule to 1933, based on the serial number of 392455. This number was issued in either 1933 or 1947 - but the "Pat. June 5,'00" label (no longer used after 1934) eliminates the latter date. The cursor on this rule, however, is a post-1937 "improved" cursor, which makes be believe it is a replacement of the original frameless cursor.

What makes this slide rule especially interesting is the name inside the case: "Bernice Carr". Women only rarely went into fields that required slide rules; so rarely that I wonder if maybe "Bernice" was a man's name at one point.

Keuffel & Esser N9081-3 Doric 10" Duplex

This slide rule is one of the Doric series, which were made out of Ivorite (Cycolac/ABS) plastic, instead of the earlier white celluloid over mahogany. K&E only used the 9xxx model numbers for a few years around 1950; that and the serial number 44063 date this slide rule to 1951.

Keuffel & Esser 68-1100 Deci-Lon 10" Duplex

The Deci-Lon slide rule was considered to be the ultimate in American slide rule development - just before the electronic calculator usurped the throne. I've actually got two of them, with cases, but no manuals. I believe they're from the 1960's. The serial numbers are 016710 and 046742.

Keuffel & Esser 4058C "Beginner's Slide Rule" 10" Mannheim

This slide rule has me a bit perplexed. It is in very fine condition - except for the broken cursor, of course - and I have the impression it is not that old. However, it has the frameless glass cursor which was discontinued in 1934. This slide rule first shows up in K&E catalogs in 1925 (for $1), described thusly:

The Beginner's Slide Rule is intended only for the use of beginners to enable them to become familiar with the slide rule without incurring the expense of obtaining the regular rule intended for professional use.

It is similar to our Mannheim Slide Rule except that the edges are not graduated. The graduations are printed on light-colored wood, and plain Directions are furnished with each rule.

According to the catalogs, this slide rule with the frameless glass cursor was available up until 1941 - seven years after the frameless glass cursor was supposedly discontinued!

It also has no serial number, but I am willing to dismiss that: part of the purpose of having a serial number engraved on the slide rule was to keep the stator and the slide, engraved on the same machine, together so as to avoid errors due to differential wear between machines. Since this rule was a cheap beginner's model, that kind of accuracy is simply not required.

Keuffel & Esser 4161-1, 5" Simplex

This slide rule and its case are in fantastic condition. I've dated this rule to 1954.

Keuffel & Esser 4097D 5" Simplex

I like this slide rule quite a bit. I've dated this rule to 1955, which is interesting because it is made of Xylonite - I've always thought Ivorite replaced Xylonite for K&E slide rule construction, because Xylonite proved to be too brittle, yet here we have a Xylonite slide rule that is newer than the Ivorite "Doric" slide rule mentioned earlier.

This slide rule is glued to the back of an Arithma Addiator; a crack down the stator behind the slide, 2/3 of the length of the rule, makes me wonder if this wasn't done to stabilize the slide rule. An Addiator was a good choice, since slide rules can't add...

Notes on Dating K&E Slide Rules

K&E put serial numbers on their slide rules starting in 1922. They recycled the numbers in 1943 and 1954, and sometime in the 1960's. Assuming production was constant, we can whip up some formulas to estimate the year a given serial number was used.

Year = 1922 + SN / 50,000

Year = 1943 + SN / 91,000

Year = 1954 + SN / 100,000

Or you can just refer to Ed Chamberlain's K&E Slide Rule Dating Chart. It's more accurate for the 1922-1943 range.

To tell which of the three above formulas to use, you need to look in the catalogs, or at other indicators of age. Such as:

1915 - Square metal framed cursors were replaced with frameless cursors using metal end blocks.
1916 - Metal end blocks replaced with plastic end blocks.
1922 - Serial numbers first applied.
1930 - Sans serif fonts replaced Serif fonts.
1932ish - Frameless cursors had flanges covering the corner of the glass.
1934 - "Pat Jun 5 '00" was replaced with "Pat 1,930,852".
1934 - Framless cursor was replaced with the "improved" cursor, which was labeled "Patent Pending".
1937 - Cursors marked "Patent 2,086,502".
1947ish - K+E logo added to right end of slide.
1947 - 90xx part numbers introduced for the Doric slide rules.
1950ish - "Keuffel & Esser Co. N.Y." replaced with "Keuffel & Esser Co."
1952 - 90xx part numbers renumbered to 41xx.
1953 - DI scale introduced
1955 - SRT scale introduced
1956 - 68-xxxx part numbers introduced

Note that these are generalizations, and may not always be correct.



© 2003 W. E. Johns