| 摘要 |
PROBLEM TO BE SOLVED: To easily reproduce an optimum state even when an optimum visibility click position is changed by providing a positioning mechanism to perform positioning to a 1st position where a 1st locking part formed on a visibility ring is engaged with a 2nd locking part inserted in/ pulled out from the 1st locking part and a 2nd position where such engagement is released. SOLUTION: A groove 7d required at the time of fixing an optional visibility click in which the click part 13a of a leaf spring 13 is fit is formed on the inner periphery side of the visibility ring 7, and the locking tooth 7a of the ring 7 is meshed with the locking tooth 4a of the click ring 4, so that click is decided by the ring 7 at an optional visibility position. A groove 7c required at the time of releasing the optional visibility click in which the click part 13a of the spring 13 is fit is formed, and the locking tooth 7a of the ring 7 is not meshed with the tooth 4a of the ring 4, so that the ring 7 releases the optional click position. The positioning mechanism is constituted of the spring 13, the click part 13a, and the grooves 7d and 7c.
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