Which movement does the original SRPD51 use?

Seiko specifies calibre 4R36: automatic with manual winding, a stop-seconds function and a day/date display. This statement covers SRPD51, not every Seiko 5 reference or a finished MedoMods watch.

Can an SRPD mod use all SKX parts?

Check each component independently against the exact reference and fitted parts. Crystal, bezel, dial, movement holder and hands require matching dimensions; a shared style or compatibility label is not a universal fit guarantee.

Does the original SRPD51 rating apply after a modification?

Seiko’s 10 bar specification describes the original SRPD51. A modification changes the assembly, so the original rating does not establish the water resistance of the finished build.

Does MedoMods sell the original SRPD donor here?

MedoMods builds and sells finished mods with their own product specifications. The linked watches are style alternatives; an original SRPD donor origin is not claimed.

SRPD Mod: plan a Seiko 5 Sports diver-style build

For an SRPD mod, start with the exact Seiko 5 Sports reference. Seiko specifies calibre 4R36 with manual winding, a stop-seconds function and a day/date display for SRPD51. Its original dimensions help with planning; replacement parts still need their own fit checks. The linked MedoMods watches are finished mods with their own specifications.

Specifications

Reference covered: Seiko 5 Sports SRPD51; check other SRPD references separately.
Original movement: SRPD51: Seiko 4R36, automatic with manual winding, a stop-seconds function and a day/date display.
Original case: SRPD51: Stainless steel; 42.5 mm diameter, 13.4 mm thickness, 46.0 mm lug-to-lug length.
Original lug width: SRPD51: 22 mm.
Original crystal: SRPD51: Hardlex.
Original water resistance: SRPD51: Seiko specifies 10 bar for the original watch; this does not establish the resistance of a modified watch.

Manufacturer sources

Seiko: SRPD51 specifications

Planning a Seiko 5 Sports SRPD (5KX) mod

Use the documented SRPD51 dimensions to plan the case proportions and bracelet.
Check the 4R36 day/date layout when choosing the dial.
Check each replacement component against the exact reference and fitted parts.

Ideas for a build

Modern diver look: a dark dial and contrasting hands, with individually checked crystal and bezel parts.
Two-tone bezel look: blue-red or blue-black colour coordination; the colours do not add a GMT function.

SRPD51 original data for build planning

The 42.5 mm case diameter, 13.4 mm thickness, 46.0 mm lug-to-lug length and 22 mm lug width describe the original SRPD51. Seiko lists Hardlex and 10 bar. A different reference or an assembled mod needs its own specifications; do not transfer the original water-resistance rating to a modified watch.

Check replacement parts instead of assuming SKX fit

Compare crystal diameter and thickness, bezel and insert dimensions, dial size, day/date openings, movement holder and hand sizes. An SKX or SRPD compatibility label alone does not establish a fit. Use the component maker’s specification for the exact reference and part.

Diver colours and real GMT functions

A blue-red or blue-black bezel is a design choice. It does not turn the SRPD51 4R36 into a GMT movement. Explore SUB for finished diver styles and GT for GMT styles, then read the functions and measurements of each MedoMods product. No original SRPD donor provenance is claimed.

Donor models Check dial design and dimensions

Donor watch questions

Which movement does the original SRPD51 use?: Seiko specifies calibre 4R36: automatic with manual winding, a stop-seconds function and a day/date display. This statement covers SRPD51, not every Seiko 5 reference or a finished MedoMods watch.
Can an SRPD mod use all SKX parts?: Check each component independently against the exact reference and fitted parts. Crystal, bezel, dial, movement holder and hands require matching dimensions; a shared style or compatibility label is not a universal fit guarantee.
Does the original SRPD51 rating apply after a modification?: Seiko’s 10 bar specification describes the original SRPD51. A modification changes the assembly, so the original rating does not establish the water resistance of the finished build.
Does MedoMods sell the original SRPD donor here?: MedoMods builds and sells finished mods with their own product specifications. The linked watches are style alternatives; an original SRPD donor origin is not claimed.