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The Encyclopedia of Horology

Glossary · Mechanism

End-stone (cap jewel)

A flat jewel closing the end of a pivot hole, against which the pivot's end shake bears.

Explanation

Fitted over a hole jewel on the balance and sometimes the escapement, the end-stone reduces friction at the pivot tip and helps control endshake. High-grade work uses curved 'olive' end-stones sitting in a shock-protection setting.