K&E 4091-3 Family of Slide Rules

An error has been noted on all of the 409x-3 series rules. The LL0 scale has an "e" at the beginning and end of the scale. It should be "e to the -1". This error was corrected by K&E between serial numbers 455535 and 460179. This correction appears to be coincident with the introduction of the New Improved Cursor. This serial number dating places this change at probably early 1935.

1933-1934 Scale set:

L LL1 DF [ CF CIF C ] D LL3 LL2  
LL0 A [ B K CI ] T S2 S1
 4091-3 --- 10" All glass cursor. Serial # 453902

4091-3 --- 10" Improved cursor. Serial # 460179

 

1934-1936 Scale set:

L LL1 DF [ CF CIF CI C ] D LL3 LL2  
LL0 A [ B K CI ] T S2 S1 
 4091-3 --- 10" Improved cursor. Serial #538852

 

1936-1937 Special Scale set for electronics calculations

L LL1 DF [ CF CIF CI C ] D LL3 LL2  
LC LL0 A [ B K CI ] T S2 S1 
 4091-3-SPEC. --- 10" Improved cursor.  Serial # 564602