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According to Sugiyama and McKeown, Tohken was the maker of the Crown (6×6) folder in the mid-1950s. The full name is given either as "Tohken Optical Works" or "Tohken Kogaku".[1] The Japanese writing is perhaps 東研光学 (Tōken Kōgaku).

Notes Edit

  1. "Tohken Optical Works": Sugiyama, item 1289; "Tohken Kogaku": McKeown, p.922.

Bibliography Edit

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