[Arran]

I'm certain you are correct, the Philco battery testers can't be all that common. I lived in Alberta for six years and have never seen or heard of such a thing, and in most places outside of the cities AC power did not exist prior to the war. I'm guessing that most service shops simply used a regular voltmeter to test batteries and couldn't see the need to buy one of those, or the customers simply tested the batteries with the radios themselves. Someone told me that the original life span of a pair of 45 Volt "B" batteries, the full sized units, was about six months with daily use, the "A"s lasted about a month.
Best Regards
Arran