Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Since you know nothing about the Exide battery, I'll hazard a guess. It's an "accumulator" cell, lead-acid type (2.2V). Such cells (technically, it's not a battery since there's only one cell) were common back in the days when people didn't always have mains-power. It would be used to power the heaters in the valves (tubes in the US) of a "wireless". When discharged, you'd take it to a hardware or wireless sales shop and they'd recharge it for a small fee - they either had mains-power or a generator. Such cells were commonly to be found is school physics labs too, I remember them from my days! They seemed to withstand the "accidental" shorts with bits of wire and other such abuse that we threw at them.