MovementSwap

Different footprints. The Miyota 8245 is 26.00 mm x 5.67 mm and the Seiko 4R34 is 27.40 mm x 5.32 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 8245 vs Seiko 4R34: do they swap?

Whether the Miyota 8245 and Seiko 4R34 share a case, and what changes if you move between them.

No drop-in

Different footprints. The Miyota 8245 is 26.00 mm x 5.67 mm and the Seiko 4R34 is 27.40 mm x 5.32 mm, so they do not share a case. This is a choice between platforms, not a swap.

The Miyota 8245 is the fullest-calendar 8200 member, with day, date and a 24-hour indicator. The Seiko 4R34 is the branded Seiko caller-GMT automatic, the retail version of the NH34.

They differ in diameter (26.00 mm vs 27.40 mm), height (5.67 mm vs 5.32 mm), calendar layout (centre seconds, day and date at 3, 24h sub-hand vs centre seconds, GMT 24h hand, date at 3), winding behaviour. An 8200-family caliber at 26.00 mm x 5.67 mm carrying day, date and a 24-hour sub-hand. It shares the family footprint with the 8205 and 8215 but needs a dial printed for its added complications.

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 824526.00 mm x 5.67 mm
Seiko 4R3427.40 mm x 5.32 mm
Donor movement for Miyota 8245drop-in lookup
Donor movement for Seiko 4R34drop-in lookup

Questions and answers

Miyota 8245 vs Seiko 4R34: do they swap?

Different footprints. The Miyota 8245 is 26.00 mm x 5.67 mm and the Seiko 4R34 is 27.40 mm x 5.32 mm, so they do not share a case. This is a choice between platforms, not a swap.