In earlier posts I highlighted a number of patented inventions that never made it to the market. The post a few days ago on the Sigell tank reminded me that there were a few inventions for 35 mm film that used the rotate in a cassette principle. I don’t think these made it to the market but I could be wrong. I only became aware of the existence of the Sigell a few weeks ago.

Here are three such patents:

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