A plurality of click portions is formed integrally with a unit body. The click portions are arranged on a common circular track, and a dial is engaged with the click portions so as to be unstable and to be prevented from slipping off. Therefore, it is not necessary to provide a D spring for coupling the dial to a shaft so as to be unstable and to be prevented from slipping off. Consequently, it is possible to reduce the number of components and a cost.