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Re:Five Hundred and Seven Mechanical Movements (1908) by dTal on Wednesday May 22, 2019 @08:55AM (#19980625)
Not just the 50s/60s - this video explaining differentials is from 1937 and is a marvel of pedagogy:

https://www.youtube.com/watch?v=yYAw79386WI

Re:Five Hundred and Seven Mechanical Movements (1908) by TeMPOraL on Wednesday May 22, 2019 @10:45AM (#19981714)
Oh yes, that's legendary! I forgot it was pre-war! Speaking of war, I also recall pretty well-made video explanations for bomber pilots, about how to fly the planes to avoid anti-aircraft fire.

So I guess I should extend my original statement to the 1930s-1970s range.