5v ish?
I don't have one in front of me. I just know that I have seen them. They let you put 2 of the 1/3N lithiums in the CCO's that take those batteries.
There is a common. One that is just a spare battery holder, and the one I used back circa 2008 that put both batteries in the circuit.
I assume the CompM4's w8de power range is a leftover from that era.