The black center part acts like a cursor on a conventional slide rule. How does it work? Watch [Chris’] video and you’ll see. We know from experience that one of these in good shape isn’t cheap.

Concise has specialized in circular slide rules, particularly for promotional distribution by other companies, since its founding in 1949. The company operated under the name Concise Co., Ltd., which ...

This last mark refers to a patent for a "slide-scale" taken out on that date by the mechanical engineer James S. Merritt of Philadelphia. The Merritt Beam Scale was mentioned in a textbook as late as ...