Caliber reference
Miyota OS20 caliber: dimensions and drop-in group
The published footprint of the Miyota OS20 and which movements share it.
Used in: a common low-cost Japanese quartz chronograph module, in analogue quartz chronographs.
A quartz chronograph at 30.80 mm x 5.10 mm with three sub-dials (24h at 3, small seconds at 6, minutes at 9) and a date at 4:30. It is a full-size chronograph module and needs a matching multi-subdial dial, not a plain three-hand swap.
Drop-in group: Miyota OS quartz chronograph (29.90 mm x 5.28 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.