20-inch Mannheim Slide Rule
Frederick Post model 1450 [1936-40]
Hemmi model 5?

No specimen available

Top edge: 
Bottom edge: 
Back of slide:
Back of rule: 

This page is from the 1936 (18th Edition) Post Catalog 
The term "adjustable" is carried over from the previous catalog in error; 
Hemmi rules did not have a friction adjusting mechanism other than the 
usual bend-able metal back plate..