What’s so special about a wooden slide rule, you ask? And indeed, for most of their 3½ centuries of existence — until the arrival of plastics — the material of choice for making slide rules has been wood… but that is the case with straight slide rules. Circular slide rules, by contrast, were almost exclusively made of metal, and later of plastic. Yet Jacob Zedak chose wood as the raw material for his take on these disc-like calculators; and he used plywood, which wouldn’t be used even in a linear rule.

Circular slide rule by Jacob Zedak

Read all about this unusual device, and about Zedak’s other products, in this new article on my History-of–Computing site.

Enjoy!