I have an optical tachometer. I checked the speed on my facetron. I wanted to have an idea of actual RPM, not just a mark on the dial. Mine was made in 2001. Doesn’t go as fast as the rated speed. I read in a couple different places that low speeds are best for polish. When I’m polishing the dial is usually set between 150 & 375 RPM. I usually use a Diamatrix lap for final polish.