Seiko VK64 (SII) caliber: dimensions and drop-in group

Used in: the bicompax meca-quartz chronograph, in two-register chronograph mods.

A bicompax meca-quartz chronograph at 30.80 mm x 5.10 mm, sharing the VK63 footprint but with two sub-dials instead of three. Its different register layout means a VK63 dial will not fit it.

Drop-in group: Seiko VK meca-quartz bicompax chronograph (30.80 mm x 5.10 mm). Matching diameter and height is necessary but not sufficient. A donor is only a true drop-in when the dial-foot positions, hand-hole sizes, stem length and calendar layout also match. Two movements can share a case and still need a new dial, re-broached hands or a cut-to-length stem.