Seiko DiaFix Cap Jewel / Bearing Jewel (受石 / Cap Jewel) – Ladies' Caliber 4L (comp. 5S / 5B / 5VE / 6SI.S / 6FA) (1 piece) – NOS

Original Seiko cap jewel / endstone (受石 / Cap Jewel, Endstone) for the DiaFix system from new old stock (NOS). This listing is for a single piece, removed from an original "SEIKO DIA FIX" packet.

DiaFix is Seiko's own mounting system for cap jewels at the pivots of the going train – typically on the escapement wheel (balance wheel) and third wheel pivots. The cap jewel (受石) is held by a spring-loaded DiaFix mount over the hole jewel, creating a defined oil reservoir at the pivot, which improves lubrication and smooth running. DiaFix was considered a quality feature of high-end Seiko movements from the 1960s/70s (e.g., King/Grand Seiko, where it was installed at numerous pivot points).

Size/Type: 4L (レディー / "Lady") → for ladies' calibers. According to the original packet, 共通 (common/compatible) for Seiko calibers 5S, 5B, 5VE, 6SI.S, and 6FA.

The part is unused; due to storage, only minor, purely cosmetic marks are possible, which do not impair function.

Manufacturer: Seiko (K. Hattori & Co., Japan).

Warranty (used) This is an original part (NOS) stored for decades. The limitation period for claims for defects (statutory warranty) is 12 months from delivery.

Note Before installation, please compare the stone dimensions (diameter/height) and the DiaFix fit with the required cap jewel; installation should be carried out professionally.