MovementSwap

Different footprints. The Seiko 6R35 is 27.40 mm x 5.25 mm and the Miyota 9075 is 26.00 mm x 4.92 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

Seiko 6R35 vs Miyota 9075: do they swap?

Whether the Seiko 6R35 and Miyota 9075 share a case, and what changes if you move between them.

No drop-in

Different footprints. The Seiko 6R35 is 27.40 mm x 5.25 mm and the Miyota 9075 is 26.00 mm x 4.92 mm, so they do not share a case. This is a choice between platforms, not a swap.

The Seiko 6R35 is the long-reserve Seiko date automatic, in higher-end Prospex and Presage models. The Miyota 9075 is the Miyota true-GMT (traveller) automatic, in affordable GMT travel watches.

They differ in diameter (27.40 mm vs 26.00 mm), height (5.25 mm vs 4.92 mm), beat rate (21,600 A/h (3 Hz) vs 28,800 A/h (4 Hz)), calendar layout (centre seconds, date at 3 vs centre seconds, true GMT 24h hand, date at 3), winding behaviour. A 27.40 mm date automatic with a 70 h reserve, slightly slimmer at 5.25 mm than the 4R35. It sits in the same 27.40 mm case family but is a Seiko-only caliber, not sold unbranded as an NH.

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

Seiko 6R3527.40 mm x 5.25 mm
Miyota 907526.00 mm x 4.92 mm
Donor movement for Seiko 6R35drop-in lookup
Donor movement for Miyota 9075drop-in lookup

Questions and answers

Seiko 6R35 vs Miyota 9075: do they swap?

Different footprints. The Seiko 6R35 is 27.40 mm x 5.25 mm and the Miyota 9075 is 26.00 mm x 4.92 mm, so they do not share a case. This is a choice between platforms, not a swap.