Seiko Cal. 6R15 is a midrange automatic movement produced by Seiko Instruments Inc. (SII) for Seiko watches. Since 2010, it is also sold by Time Module Inc. (TMI) as Cal. NE15 for use by other manufacturers. Although not a high-beat movement, it is more refined and accurate than the related Seiko 4R series and uses a Spron 510 mainspring for 50 hour power reserve. Cal. 6R35 is similar but with a longer 70 hour power reserve.
The original movement was Cal. 6R15A, but this was updated with unspecified replacement parts as Cal. 6R15B. Cal. 6R15C has additional new parts but retains the case spring at 8:00 for use in A/B watches, while Cal. 6R15D lacks this spring but is otherwise similar.
Cal. 6R15 was introduced around 2006 and remains in production today. It has 23 jewels and 168 parts. Cal. 6R15 was used in the Premier Automatic watches, models SPB007J1, SPB009J1, and SPB011J1, produced October 2007 through July 2011.
Seiko builds Cal. 6R20, 6R21, 6R24, and 6R27 using modules on the 6R15 base. These movements also use a Hi-Beat 28,800 A/h balance.
Seiko 6R15 Applications
As of 2020, Seiko uses Cal. 6R15 in some higher-end Presage and Prospex models.
- Seiko Presage SPB047
- Seiko Presage Tonneau SPB049
- Seiko Prospex Diver’s 200M SPB051, SPB053, SPB071
- Seiko Prospex Diver’s 200M SPB077, SPB097, SPB105
- Seiko Prospex Diver’s 200M SPB079, SPB087
| Jewels | Components | Speed | Power | 3:00 | 6:00 | 9:00 | |
| 6R15 | 23 | 168 | 21,600 | 50 | Date Window | ||
| 6R20 | 29 | 208 | 28,800 | 45 | Day Subdial | Date Subdial | Clockwise Power Reserve |
| 6R21 | 29 | 208 | 28,800 | 45 | Day Subdial | Date Subdial | Counter-Clockwise Power Reserve |
| 6R24 | 31 | 224 | 28,800 | 45 | Retrograde Day | Retrograde Date | Clockwise Power Reserve |
| 6R27 | 29 | 28,800 | 45 | Date Subdial | Counter-Clockwise Power Reserve | ||
| 6R35 | 24 | 21,600 | 70 | Date Window |