SR626SW vs SR626SW
The SR626SW and the 377 are the same battery. SR626SW is the IEC code (silver oxide, round, 6.8 mm by 2.6 mm, low-drain type) and 377 is the retail number every battery counter uses. Any brand's cell carrying either marking fits and performs identically.
| SR626SW | SR626SW | |
|---|---|---|
| Chemistry | Silver oxide (Ag2O) | Silver oxide (Ag2O) |
| Voltage | 1.55 V | 1.55 V |
| Diameter | 6.8 mm | 6.8 mm |
| Height | 2.6 mm | 2.6 mm |
| Capacity | 25-28 mAh | 25-28 mAh |
| Also sold as | 377, SR66, V377, D377 | 377, SR66, V377, D377 |
Battery packaging piles up codes because different industries standardized separately: watchmakers order by the 377 number, engineers specify SR626SW, German brands print V377, and Seiko service sheets use their own references. All of it converges on one physical product, which happens to be among the best-selling watch batteries in the world thanks to decades of small quartz movements designed around it.
The only genuine variant is the 376, or SR626W, the high-drain version of the same case. The W-type electrolyte handles current pulses from backlights, alarms and chronograph motors; the SW-type maximizes life at the microamp drains of plain analog watches. Fitting either in the other's role works, at a small cost in longevity. If your watch is a simple two- or three-hander, the 377 is the right and default choice.