Technical sheet
Sellita’s 7750-architecture automatic chronograph: counters at 12 and 6, small seconds at 9.
Features
Going train
| Arbor | Wheel | Pinion | True speed |
|---|---|---|---|
| Mainspring barrel | 84 | — | 1 rev / 7 hours |
| Center wheel | 80 | 12 | 1 rev / hour |
| Third wheel | 75 | 10 | 8 rev / hour |
| Fourth (seconds) wheel | 84 | 10 | 1 rev / minute |
| Escape wheel | 20 | 7 | 12 rev / minute |
Disclaimer
An approximation of the Sellita SW500 layout from public drawings and photographs, not a manufacturer-accurate replica. 28,800 vph (4 Hz), 25 jewels, typical 62 h power reserve, Ø 30.00 mm casing diameter (30.40 mm overall), 7.90 mm height, self-winding on a ball bearing, cam-operated chronograph with two push buttons, small seconds at 9, 30-minute counter at 12, 12-hour counter at 6, day and date with quick setting and stop-seconds are Sellita’s published figures for the SW500 a. Sellita does not state the winding direction or the coupling type: the model reuses the Valjoux 7750 arrangement (oscillating pinion) of which the SW500 is described as an almost direct clone. Tooth counts, wheel sizes and the outlines of bridges and chronograph parts are an approximation. The escapement and chronograph motions are kinematic models.