CX726S,V396, V397, SG2, 396, 532, 536, 556 Silver Oxide Button Cell  1.55V High Capacity.

Typically for watches & calculators and miniature equipment 7.9 X 2.6mm. Equivalent to Timex V

Note: Battery Iilustrations are for identification only. Type numbers and manufacturers may vary. All batteries are high quality brands