Circular Slide Rule

[SlideRule]

Do you have 4 units, with one of those in each unit?
No, I have one (1) unit w/ three (3) additional inserts

Also, what is the star for? It's present on the upper right corner on one side of all of them …
A star is on the upper left of the front side of the unit; I align the star on the insert to match the star on the unit

According to the manual for;
Model 600 series;
… INSERT-CE for chemical & mechanical engineers & chemists
… INSERT-ST for science students
Model 200 series;
… INSERT-EE for electrical & electronic engineers
CIBA Medical
… INSERT-MM for medical students & nurses ?

I received my order on 11 JUL '77 from SAMA & ETANI, Groton Massachusetts at Kansas State University while completing a degree in Civil Engineering.

BEST!
SlideRule