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The Encyclopedia of Horology

Glossary · Mechanism

Cap stone (end stone)

A flat jewel closing the end of a pivot hole, against which the pivot tip bears.

Explanation

A cap stone (end stone) is a flat jewel placed over a hole jewel so that the end of a pivot bears on it. It reduces friction when the watch is in dial-up or dial-down positions and holds oil in place. Cap jewels are typical on balance and often on escape and pallet pivots of better watches; jewel counts above 15 usually include cap stones.