364 - SR60, 20mAh, 1.55V, Silver-Oxide
Whatever kind of watch you have, it's likely that one of these silver oxide button batteries can power it.
Duracell 364, Single-use battery, SR60, Silver-Oxide (S), 1,5 V, 1 pc(s), Button/coin
Duracell 364. Battery type: Single-use battery, Battery size(s): SR60, Battery technology: Silver-Oxide (S). Battery form factor: Button/coin