Drop-in resolution
Seiko VK63 (SII) vs Seiko VK67 (SII): do they swap?
Whether the Seiko VK63 (SII) and Seiko VK67 (SII) share a case, and what changes if you move between them.
Close in diameter, not a drop-in. The Seiko VK63 (SII) (30.80 mm x 5.10 mm) and Seiko VK67 (SII) (30.80 mm x 5.10 mm) are near in size but differ in height, dial feet or layout, so moving between them means a new dial, hands and often a case adjustment.
The Seiko VK63 (SII) is the reference meca-quartz chronograph for modders, a quartz base with a mechanical chrono module. The Seiko VK67 (SII) is a no-date bicompax meca-quartz chronograph with a symmetrical 3-9 layout.
They differ in calendar layout (meca-quartz chronograph, three sub-dials, date vs meca-quartz chronograph, two sub-dials at 3 and 9, no date). A meca-quartz chronograph at 30.80 mm x 5.10 mm: quartz timekeeping with a snap-back mechanical chronograph. It has three sub-dials and a date; the VK64 is its bicompax relative with a different sub-dial count.
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.