379 (SR521) Watch Batteries
The 379 button cell is a watch battery that directly replaces the 379, SR521, SR521SW, SR63, RW327, D379, V379(520), 28059, and SB-AC. It features a small footprint, and has a fairly low capacity. It is commonly used in small watches with few functions.
These cells utilize silver oxide chemistry. The case is 5.8mm in diameter and 2.1mm thick. Voltage supplied is 1.55V and the typical capacity is about 15mAh.