All of us over a certain age will have used one of these -
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The switch was their Achille's heel, it operated a sprung contact across the batteries which was forever either refusing to do it's job or breaking off. A hard thump on the body was often enough to make it behave for a while.
This thread has made me think that in spite of all the wonderous mechanical advances on modern bikes it is the lights that have made the greatest leap in terms of quality and effectiveness.
New fangled modern stuff!
My first bike light was carbide powered !
(I think it came off my Dad's childhood bike, I was the only kid at school with one and even the teachers commented on it)