PURPOSE: To obtain a zero setting mechanism that is free from any variance of engagement between the 1st gear and an intermediate gear, by forming a coarse surface for the revolution transmitting part of the intermediate gear and at the same time forming the revolution transmitting part of a gear to be driven with a material having a high coefficient of friction.

CONSTITUTION: During the revolution, an intermediate gear 1 engages between the 1st gear 3 and a dial pate gear 4 to which the revolution is transmitted from a revolving pinion 2. This engagement of the gear 1 is released when zoro is set, and the dial plate gears 4, 5 and 6 are reset to each figure of zero. Then an engagement is given again to the gear 1. The working of a thin rib or satin finish is applied to a revolution transmitting part 1-2 of the gear 1 to the gear 3. And the rubber or the like material having a high coefficient of friction is used for a revolution transmitting part 3-1 of the gear 3. As a result, the revolving variance is eliminated among these gears.