This sale is for a new old stock vintage 1944 AC mechanical tachograph. This tachograph fits early 1940's GMC trucks. Note that the measurement is in hundreds, not thousands. 0-10 or 0-1000 rpm. The information on this item is: Made in USA. - AC div. G.M.C. -1536140 Registers cable speed - and what appears to be Jun 14 1944. On the face of the gauge- RPM hundreds - Revolutions thousands. 1-10. Housing diameter is 3 3/8 inches.