5.21 Unidentified

Assuming the other identifications within the collection have all been “correct,” the list produced here contains slide rules in the collection for which to date I have not been able to positively identify their makers. Fairly detailed depictions are presented in order for others to view and possibly help in determining their proper maker’s identity.


Gunter Rule.

Printer’s Proportions Rule.

Unidentified Rule from Japan.

Total number of unidentified slide rules in the collection: 3.

Reminder: L0 is the length of a decade on the main scale; Lx is the overall length of the slide rule.

Model Year Mat L0 Lx Case Note
Gunter Rule
1820 wd 12 24 no nice condition; clear standard Gunter scales and brass pins
Engraving Rule
1940 wd 12 20 no 18 inch proportions rule, perhaps used in printing, engraving; maker? American Blueprint? (similar construction to U.S. Military Rule); A/B scales range from 1 to 30, 12 inches from 1 to 10
1970 pl 5 5 no Made in Japan; ALCO?; from my high school years; note C and rho gauge marks