Noone has mentioned the flat 4.5 V flashlight battery.? It was very common when I was growing up in Sweden.

The size was 65 x 60 x 23mm and fit nicely in a pocket.

See:

Often the lamp was at the end, not sideways.

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The other flashlight I remember was hand-powered by squeezing a lever.? There was no battery, so it was a hand exerciser.

It fit nicely in the hand.? Not like the models sold with and external crank to turn.

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Bertho