On Mon, 17 Jul 2017 05:00:55 -0400, oldschool wrote:

I do have to ask, why these meters used BOTH the D cells and other
batteries as well. (In other words, more than one kind of battery). Why
didn't they just use one battery or one set of batteries for the whole
device?


Dunno. I'm sure someone here will, though.
Fortunately, although 15V batteries are largely unobtainium these days,
10x1.5V AAA cells will get you there and the battery compartment is
capacious enough (AVOs are anyway) to house them all comfortably.