| Manufacturer | S. Epson (Seiko owned) |
| Caliber Number | YM04A |
| Movement Type | Quartz, battery-powered |
| Movement Class | Chronograph, big-date |
| Lignes | 12”’ |
| Diameter | 27mm |
| Height | 4.93mm |
| Jewel Count | 0 (no jewels) |
| Frequency | 32,768 Hz |
| Accuracy Rating | +/- 20 seconds/month |
| Battery Cell | SR927SW (395/399) |
| Battery Life | 5 years |
| Regulator? | None |
| Hand Count | 6 |
| Hand Sizes | 1.10mm / .65mm / .21mm / .21mm x 3 |
| Functions | Central hours; central minutes; central chronograph hand; small seconds hand at 9:00; 60 minutes chronograph counter at 6:00; 24 hour indicator at 3:00, big double digit date at 12:00 |
| Hacking Seconds? | Yes |
| Country of Manufacture | Made in Japan |
| Known Models | Invicta Aviator (model 1233) (Add your watch to the comments below…) |
Seiko Epson caliber YM04A is a quartz chronograph watch movement with a big date and 24 hour indicator.
Examples of watches with this movements:
This example of cal. YM04A was found in an Invicta Aviator watch. Notice the extra long chronograph pusher stems needed to accommodate the 27mm movement in a 48mm diameter case.
Additional Resources:
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