Tōkyō Kōgaku (maker of the Topcon cameras) made lenses in 39mm Leica mount for some Japanese Leica copies, mainly the Leotax. All were all chrome unless noted. The chronological order is State - C Simlar - Simlar - Topcor - Topcor S.
- 35/2.8 Topcor, sold with a very big external finder
- 50/3.5 State (collapsible)
- 50/3.5 C Simlar (collapsible)
- 50/3.5 Simlar (collapsible), also as "Simlar 1:3,5 f=5cm Tokyo Opt. Co."
- 50/3.5 Topcor (collapsible), diaphragm ring around the front lens, then around the barrel
- 50/3.5 Topcor K (rigid), aluminium barrel and knurled rings
- 50/2.8 Topcor,(rigid) black and chrome finish. (Heliar) Optical design is a copy of the 1952 Voigtländer (R&D) "Color Heliar" (Extremely rare lens due to very low production numbers)
- 50/2 Topcor
- 50/2 Topcor S, chrome, then black and chrome, then black with aluminium barrel
- 50/1.8 Topcor S, black finish
- 50/1.5 Simlar
- 50/1.5 Topcor
- 9cm f/4 C Simlar
- 90/3.5 Topcor, aluminium barrel and knurled rings, sold with an external finder
- 135/3.5 Topcor, aluminium barrel, sold with an external finder with 50/90/135 frames
- Tōkyō Kōgaku 39mm screw lenses at the Topcon Club website
- Pages of Nekosan's website:
- Topcor 5cm f/2 and Topcor-S 5cm f/2 in Kensetsu's camera collection
- Topcor 3.5cm f/2.8, Topcor 5cm f/3.5 and Topcor-S 5cm f/2 at Koujiya's blog
- Topcor-S 5cm f/2 and Topcor 9cm f/3.5 at Lens Paradise
- Topcor-S 5cm f/2 at Fukugawa Seimitsu Kōbō
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