This is a vintage transistor radio, likely using a carbon-zinc battery (LeClanche Cell). They use an acid-based electrolyte. As carefully detailed. Latter-day batteries *tend* to use alkaline-based electrolytes - making most of the discussions herein accurate. But - not in all examples of all cases.

I try to advise based on good chemistry based on the data as presented.

Peter Wieck
Melrose Park, PA