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WatchtheDetails

Movement comparison

7S26 vs 4R36

same diameter; 0.42 mm taller. Can 4R36 replace 7S26? Only with changes to the watch or parts. Some fit figures are still unpublished, so this verdict is not confirmed.

Sources checked · How we source numbers
Movements to scale: Seiko 7S26, Seiko 4R36Dial side and side section at one scale, hand holes enlarged 8:1. A Seiko 7S26: Ø 27.4, H 4.9, date 3H, crown —. B Seiko 4R36: Ø 27.4, H 5.32, date 3H, crown — (vs A: Ø 0 H +0.42 mm).A Ø 27.4B Ø 27.4A 4.9B 5.32SIDE · HEIGHTS ON ONE BASELINEHAND HOLES · 8:1A hour 1.5 · minute 0.9 · second 0.21B hand holes —A Seiko 7S26Ø 27.4 · H 4.9 · date 3H · crown —B Seiko 4R36Ø 27.4 · H 5.32 · date 3H · crown —vs A: Ø 0 H +0.42 mm
7S26 vs 4R36 to one scaleDrawing from data, not a photo · mm

Published figures

Differences are highlighted. Each number links to its source; an empty field says what is missing.

7S26 vs 4R36 specification comparison
FigureASeiko 7S26BSeiko 4R36
Diameter27.4 mm1seller listing27.4 mm3secondary source
Casing diameterone side only27 mm1seller listingnot in the documents we read
Heightdiffers4.9 mm1seller listing5.32 mm3secondary source
Jewelsdiffers214244
Beat rate21,600 bph421,600 bph4
Power reserve41 h441 h4
2 sources disagree; show every value
  • manufacturer 41 h4
  • secondary source 40, 41 h3
Accuracy (maker)one side onlynot in the documents we read−35 to +45 s/day5
Hands and functionshours, minutes, centre seconds, date, day4 · date, day2hours, minutes, centre seconds, date, day4
Hacking secondsone side onlynot published by SeikoYes4
Hand windingone side onlynot published by SeikoYes4
Date window3H2secondary source3H3secondary source
Do not set the date21:00–04:00421:00–04:004
Hand holesone side onlyhour 1.5 · minute 0.9 · second 0.21 mm1seller listingnot published by Seiko

Can 4R36 replace 7S26?

The direction matters: this checks a watch built for the first calibre with the second installed. Size alone does not prove that hands, dial, stem and case will fit.

Fits with changes· not confirmed
  • =diameterSame movement diameter: 27.4 mm.
  • ≠height4R36 is 0.42 mm taller (5.32 mm vs 4.9 mm): check the room under the crystal and the case back; the hands sit higher.
  • =dateDate window at 3H on both.

Not published, so not checked: hand holes for 4R36; crown position for 7S26; crown position for 4R36; dial feet for 7S26; dial feet for 4R36.

Check the actual case, stem height and parts before ordering. Compare another pair.

Sources

Documents checked · Report a wrong number

  1. 1Esslinger & Co. — Genuine Seiko 3 Hand Automatic Watch Movement 7S26 (product page, movement marked 7S26C) · html · read
  2. 2Grail Watch — Grail Watch Reference: Seiko Cal. 7S26 · html · read
  3. 3Grail Watch — Grail Watch Reference: Seiko Cal. 4R36 · html · read
  4. 4Seiko Watch Corporation — Instructions: Seiko Automatic Diver's Watch Cal. 4R15/4R16/4R35/4R36/7S26/7S35/7S36 (English) · pdf · read
  5. 5Seiko Watch Corporation — Instructions: Diver's Watch for Air Diving, Cal. 4R35 / 4R36 (English) · pdf · read
  6. 6Seiko Watch Corporation — Instructions: Mechanical watch, Cal. 4R35 / 4R36 / 4R37 / 4R38 / 4R71 / 4R72 / 4R39 (English) · pdf · read