LR927 vs SR927SW
The LR927 and the SR927 both measure 9.5 mm across and 2.7 mm tall, so they swap freely. The LR927 is 1.5 volt alkaline with 40 to 50 mAh. The SR927SW, sold as the 395, is 1.55 volt silver oxide with 52 to 57 mAh and a far steadier output under load.
| LR927 | SR927SW | |
|---|---|---|
| Chemistry | Alkaline (Zn/MnO2) | Silver oxide (Ag2O) |
| Voltage | 1.5 V | 1.55 V |
| Diameter | 9.5 mm | 9.5 mm |
| Height | 2.7 mm | 2.7 mm |
| Capacity | 40-50 mAh | 52-57 mAh |
| Also sold as | AG7, LR57, LR926, L926 | 395, SR57, V395, SR927W (399, high drain) |
Start with the labels, because this size carries plenty of them. The alkaline sells as LR927, AG7, LR57, LR926 and L926, and the LR926 and LR927 markings are the same battery, differing only in how a maker rounds the nominal height. The silver version appears as SR927SW, 395, SR57 and V395, with SR927W, the 399, as its high-drain twin.
The reason this pairing matters more than most is the 399. Stopwatch motors pull short bursts of current well above the microamps a resting watch uses, and an alkaline AG7 cannot hold voltage through them, so chrono hands stutter, subdials stall or the movement resets. The low-drain 395 copes better but is not built for that load either. Chronographs and sports watches want the 399.
For plain analog watches in this size the 395 is the normal fit, and its 52 to 57 mAh runs a simple movement two to three years. A chronograph on a 399 sits closer to two, less if you use the stopwatch often. The alkaline earns its place in small LED lights and toys, where a sagging 1.5 volts costs nothing but a little brightness.