Cal. 61 was a family of mechanical watch movements produced by Suwa Seikosha for Seiko-branded watches from the late 1960s through the 1970s. It was an advanced and popular movement, supporting complications and high-end watches as well as more mainstream models.
The bi-directional automatic winding system in the 61 stream movements uses Seiko’s Magic Lever system rather than a traditional reverser gear.
Suwa Seikosha 61 Stream Standard Movements
| Production | Jewels | Date | Notes | |
|---|---|---|---|---|
| 6105A 6105B | 1968-1977 | 17 | Date | |
| 6106A 6106B 6106C | 1967-1977 | 23 25 | Day/Date | |
| 6117A 6117B | 1968-1977 | 17 | Date | Central 24 Hour Hand |
| 6119A 6119B 6119C | 1967-1976 | 21 | Day/Date | |
| 6138A 6138B | 1970-1979 | 23 | Day/Date | Speed-Timer 30-Minute and 12-Hour Chronograph |
| 6139A 6139B | 1969-1979 | 21 | Day/Date | Speed-Timer 30-Minute Chronograph |
Suwa Seikosha 61 Stream Hi-Beat Movements
| Production | Date | Rating | Notes | |
|---|---|---|---|---|
| Cal. 6145A | 1968-1970 | Date | GS Standard | |
| Cal. 6146A | 1968-1970 | Day/Date | GS Standard | |
| Cal. 6155A | 1970-1973 | Date | GS Special | |
| Cal. 6156A | 1970-1973 | Day/Date | GS Special | |
| Cal. 6159A | 1968-1974 | Date | Diver 300 | |
| Cal. 6159B | 1975-1979 | Date | Diver 600, hacking seconds | |
| Cal. 6185A | 1969-1972 | Date | VFA | |
| Cal. 6185B | Date | VFA | Hacking seconds | |
| Cal. 6186B | 1972-1975 | Day/Date | VFA | Hacking seconds |