Talk:Overhead projector

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Can we get a timescale? They were common up to the 1990s, but when did they first appear? -- Tarquin 20:47, 30 Aug 2003 (UTC)

Likewise, I learned in a technology-in-the-classroom class that they were introduced in the early 1940s by the US military for training purposes. Is there a patent application somewhere? Daniel Case 07:32, 11 February 2006 (UTC)

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