The Fowler Long Scale was manufactured in the late 1800s and the late 1900s, it was a type of circular slide rule shaped like a pocket watch. It had a front and a back with sets of circles that could be rotated with 2 knobs on the top of it. The front had a short and a long logarithmic scale made up of 6 rotating paper circles, but the back was a for division, multiplication, reciprocals, etc. It was made up of 7 circles rotated with the other knob.
The Fowler Long Scale was manufactured by Fowler Calculators which was a company based in Massachusetts which was known for its engineering pocket books which were created when the company was called "The Scientific Publishing Company".
Fowler Long Scale Pocket Slide-Rule Source: Collectingme.com
Also check out the Otis King Slide Rule.