| Brand: | Seiko, Seiko Instruments Inc., Time Module Inc. | 
|
|---|---|---|
| Family: | ||
| Height: | 5.32 mm | |
| Jewels: | 24 | |
| Reserve: | 40 hours | |
| Frequency: | 21600 A/h | |
| Winding: | Automatic, Bi-Directional Automatic Winding | |
| Diameter: | 27.40 mm (12 ligne) | |
| Complications: | Hacking Seconds, Hand Winding | |
| Hands: | Central Hour Hand, Central Minute Hand, Central Seconds Hand, Open Heart at 9:00 | |
| Production: 2018 – Current | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| 1910s | 1920s | 1930s | 1940s | 1950s | 1960s | 1970s | 1980s | 1990s | 2000s | 2010s | 2020s |
Seiko Cal. 4R71A (commonly called just Cal. 4R71) is a partially-skeletonized and open heart mainstream automatic movement. It is also offered by Time Module Inc. (TMI) as Cal. NH70A and NH71A (gold plated) for use by other watch makers. It is closely related to the date-only Cal. 4R35 and 4R38.
First appearing in late 2017 for the 2018 BaselWorld releases, Cal. 4R71 has only been used in two limited-edition Seiko Premier watches.
Hand winding is accomplished with the crown in first position, rotating clockwise.
| Traditional Mainspring Hacking/Hand-Winding | Spron 510 Mainspring | |
| Standard | 4R38A NH38A 4R71A (skeleton) NH70A (skeleton) NH71A (skeleton, gilt) | |
| Date | 4R35A 4R35B NH35A | 4R15A 4R15B NH15A |
| Day and Date | 4R36A NH36A | 4R16A 4R16B NH16A |
| Date, 24 Hour Subdial | 4R37A NH37A | |
| 24 Hour Subdial | 4R39A NH39A | |
| Date by Pointer Power Reserve | 4R57A |
