K&E 4104 --- 20" Mystery Slide Rule

A Special Production Slide Rule of Military Use

This rule is a strange variation of a 4053-5 Mannheim style slide rule. The L scale has been moved to the front of the rule displacing the K scale which was moved to the front edge of the rule like the 4053s before 1922. Also a second A scale is placed between the S and T scales on the back side of the slide. Both the S and T scales are referenced to the A scale and are in decimal degrees rather than the normal degrees/minutes/seconds division of the 4053s. The rule also has a new model number which makes it interesting. This model number is not referenced in any K&E catalog. The serial number, case style and cursor style indicates that the rule was produced between 1945 and 1946 or 1955 and 1956 depending on which serial number rollover applied. The serial number is: 044178

Having the trig scales divided in decimal degrees suggest that the rule had military uses. In the 1950s and 1960s the US military had K&E produce a special version of the 4053-3 (D4053-3) with the trig scales divided in decimal degrees.

Update: In surveying the Tom Wyman collection recently two more of these rules have been discovered. One is marked 4104 and has a serial number of 044071. The second is unmarked with a model numbers but is identical to the other two and has a serial number of: 925411. The unmarked rule probably was produced about 1 to 2 years before the two marked ones. The two marked ones are probably from the same manufacturing batch.

This slide rule is from the collection of Ron Knapp.

Scans by Ron Knapp.

Front Side

Back Side

Back of Slide

Cursor Details

End View of Scales

Case