Kafu Seiko Co. was perhaps a Japanese lens maker. The name Kafu Seiko Co. appears on the lenses of the Topflex and Honestflex, name variants of the Vesterflex made by Ginrei Kōki. (This is certainly why the Honestflex is attributed to Kafu by Sugiyama.) These markings also include a fake serial number, which seems to be 872728 in all cases, whether on the taking or on the viewing lens, and the company name "Kafu Seiko Co." might be a fake too.
- Sugiyama, Kōichi (杉山浩一); Naoi, Hiroaki (直井浩明); Bullock, John R. The Collector's Guide to Japanese Cameras. 国産カメラ図鑑 (Kokusan kamera zukan). Tokyo: Asahi Sonorama, 1985. ISBN 4-257-03187-5.
- Takasaki Akio (高崎晶夫). "Kokusan 6×6cm-han nigan-refu A to Z" (国産6×6cm判二眼レフA to Z, Japanese 6×6cm TLR A to Z). Kamera Rebyū: Kurashikku Kamera Senka (カメラレビュー クラシックカメラ専科) / Camera Review: All about Historical Cameras no.49, December 1998. ISBN 4-257-13022-9. Amerika-sei 35mm renzu-shattā kamera (アメリカ製35mmレンズシャッターカメラ, issue about American 35mm lens-shutter cameras). Pp.64–73.