K&E 4091-3 Family of Slide Rules

1933-1934 Scale set:

L LL1 DF = CF CIF C = D LL3 LL2  
L00 A = B K CI = T S2 S1 

1934-1936 Scale set:

L LL1 DF = CF CIF CI C = D LL3 LL2  
L00 A = B K CI = T S2 S1