Seiko 7A28 Movement Details
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| Sub-brands: | Sports 100, Speedmaster, SQ |
| Battery: | SR936SW / 394 (Silver oxide) |
| Accuracy: | ±15 seconds/month |
| Day / date? | No |
| GMT / world time? | No |
| Chronograph? | Yes |
| Alarm? | No |
| Hacking? | Yes |
| Rate: | 32,768 Hz |
| Number of jewels: | 15 |
| Size / diameter: | 29.0mm |
| Height: | 3.5mm |
| Development division: | Suwa (Nagano Prefecture, Japan) |
| Notes: | The world's first analog quartz chronograph and, unlike many other quartz chronographs, uses metal rather than plastic parts making it fully serviceable. Used in watches supplied to the British and South African air forces. Has a battery life indicator function. The same as cal. 7A38 but without day and date display. |
| PDF guides: | Technical guide : 7A28A |
| Related movements: | 7A34 7A36 7A38 7A48 7A54 |
Part Codes
| Stem code: | 354726 |
| Screw codes: | 022233 (dial screw), 022286, 022341, 022424 |
Videos
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- Seiko 7A28 Collector’s Guide [thespringbar.com]
- Seiko 7A28 Pt 2: The Quiet Beauty [wornandwound.com]
- 7A28 Service Hints? [thewatchforum.co.uk]
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