MovementSwap

Different footprints. The Miyota 9075 is 26.00 mm x 4.92 mm and the Seiko 6R15 is 27.40 mm x 5.25 mm, so they do not share a case. This is a choice between platforms, not a swap. Published dimensions, layout and the checks before you swap one for the other.

Updated 05 September 2026.

Drop-in resolution

Miyota 9075 vs Seiko 6R15: do they swap?

Whether the Miyota 9075 and Seiko 6R15 share a case, and what changes if you move between them.

No drop-in

Different footprints. The Miyota 9075 is 26.00 mm x 4.92 mm and the Seiko 6R15 is 27.40 mm x 5.25 mm, so they do not share a case. This is a choice between platforms, not a swap.

The Miyota 9075 is the Miyota true-GMT (traveller) automatic, in affordable GMT travel watches. The Seiko 6R15 is the predecessor of the 6R35, a date automatic in earlier Prospex and Presage models.

They differ in diameter (26.00 mm vs 27.40 mm), height (4.92 mm vs 5.25 mm), beat rate (28,800 A/h (4 Hz) vs 21,600 A/h (3 Hz)), calendar layout (centre seconds, true GMT 24h hand, date at 3 vs centre seconds, date at 3), winding behaviour. A 90-series-based true/traveller GMT at 26.00 mm x 4.92 mm with an independently-set local hour hand and a 24-hour GMT hand. Taller than the time-only 9015, it needs a GMT dial and hand set of its own.

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.

Calibers and lookups

Miyota 907526.00 mm x 4.92 mm
Seiko 6R1527.40 mm x 5.25 mm
Donor movement for Miyota 9075drop-in lookup
Donor movement for Seiko 6R15drop-in lookup

Questions and answers

Miyota 9075 vs Seiko 6R15: do they swap?

Different footprints. The Miyota 9075 is 26.00 mm x 4.92 mm and the Seiko 6R15 is 27.40 mm x 5.25 mm, so they do not share a case. This is a choice between platforms, not a swap.