The 7R31 K Battery 4 volt is a vintage part that is highly sought after by 110 film enthusiasts. This long-discontinued battery is used as a donor part for repairing or restoring vintage cameras. This a spent/dead 7R31 battery (PX31/K-type) battery—discontinued but intact and highly sought as useful as a donor shell for DIY repurposing (many 110 enthusiasts cut them open and fit three LR44/AG13 button cells for a working 4.5V equivalent—look for videos online). At this price it is less than half the cost of buying a rare adapter. NB the battery is spent.
