The Zeiss 50mm f/0.7 Planar was not the only f/0.7 lens of the period. There was also the Simlar 50mm f/0.7. The Simlar lenses were made by Tokyo Kogaku, which would eventually become Topcon (Japan). The original lens was designed by Maruyama Shūji. The story of the lens originates from the December 1951 issue of Asahi Camera [1]. It was ordered by the Japanese Army for use in nighttime reconnaissance photography, and was completed in 1944. Before it could be used for its intended purpose, the copies of the lens were claimed by the Aeronautical Engineering Institute of Tachikawa for X-ray medical photography. The article suggests ten copies were made by wars end, but their fate is unknown except for one lens kept by Maruyama Shūji.

A second, postwar version of the camera was produced in 1951 – the dimensions and the weight had both changed (123.7mm×105mm ∅, 2.5kg). Only three copies of the lens were made, of which two were supposedly used on a Antarctic expedition by the Mainichi Newspaper. The Trade and Industry of Japan publication from 1955 shows the lens.

The strange thing about the second series is that the weight of the lens changed from 1kg to 2.5kg, which is a substantial increase. I would beckon to suggest that the design of the original series was copied from either the wartime Zeiss objective, or perhaps the Herzberger objective. When the war was over, there was either issues with using the patent, or an inability to obtain the proper glass, adding extra weight. However there does not seem to be any surviving pictures of the second series.

For those interested, here is a link to another lens, the Simlar-F 180mm f/1.5 produced in 1942. It provides a sense of the aesthetics of the Simlar lenses.

Further reading:

1. Asahi Camera December 1951. “Toki no wadai: Hachi-nen mae ni Nihon de dekite ita F0.7 no renzu” (時の話題・八年前に日本で出来ていたF0.7のレンズ, Topic of the time: An f/0.7 lens made in Japan eight years ago). P.84.
2. Topcon Club – Lenses