This is the large large battery box (uses six 1.5-volt "C" size alkaline batteries-user supplied) that can be used with LaGard locks that require external power.
There is also...
Duracell 3-Volt Lithium Battery (DL1/3N)
FITS MOST ELECTRONIC TIME MOVEMENTS
Also commonly used in key fobs, wristwatches, hearing aids, digital calipers/tools, small flashli