Superior Maxell 391 SR1120W Micro Silver Oxide
381 and 391 are completely interchangeable with identical functionality
Superior Maxell Micro Silver Oxide SR1120W One Battery
Do not use (inherently low performing) alkaline batteries in place of silver oxide in any timepiece.
Made in Japan
Genuine Maxell Hologram Anti-Counterfeit Packaging (other package is not genuine)
Dimensions 11.6mm Diameter x 2.0mm Height
1.55 volts 55 mAh
This is a primary non rechargeable disposable battery
The 391 is a long life silver oxide chemistry with non-declining power output; alkaline batteries of the same 1.5 voltage start at 1.5 and at the half life are at .8 volts, silver oxide start at 1.55 volts and maintain the voltage until expiring. This is why silver oxide batteries are always used in watches, insulin pumps and sniper scopes or mission critical situations. Never use alkaline batteries for any device requiring a steady constant voltage. A watch with declining voltage cannot give the correct time.
Fits and Replaces:
This is from the American Watchmakers-Clockmakers Institute 2008 Edition Handbook "Battery Number System". This Battery is cross-referenced as: AWCI S11, Energizer (UCAR) 391, Citizen 280-30, Duracell D391/D381, Duracell D381/D391, Duracell D391, Duracell D381, Duracell 10L130, Mallory D391/D381, Mallory D381/D391, Mallory D391, Mallory D381, Mallory 10L130, Gold Peak GP91, Sylva-Cell GP91, Maxell SR1120W, Maxell G8, Panasonic SP391, Panasonic SR1120W, Panasonic WL-5, National SP391, National SR1120W, National WL-5, Rayovac 391, Rayovac RW40, Renata 391, Renata 23, Seiko SR1120W/TR1120W, Seiko SB-BS, Seiko SB-ES, Sony SR1120W, Sony 391, Toshiba SR1120W, Toshiba W1K, Varta V391, Varta 553