Tokyo Kogaku started in 1933 as a specialist optical producer. The compagnies focus was on the production of optical devices for the Japanese government. In the years to follow before 1939 a series of lenses were produced which were used in some of the early Japanese plate and folding cameras.
Although the company designed and manufactured in 1937 it first camera: the Lord, the main production for the photographic market were these State, Simlar, and Toko lenses. 1935 Ohara Optical Glass was acquired by the firm , which supplied for the glass. A durable allegiance with Seikosha also originated from the beginning of the company. From this age the also the TOKO logo originated, by which nowadays the origin of older products can be determined.
Simlar lenses were made by Tōkyō Kōgaku from c.1935 to 1955. The name Simlar (written shimurā in Japanese) is derived from Shimura (志村), a place name in Tokyo where the company plant was located. The Simlar brand was originally used for a four-element lens design, copy of the Tessar. From the late 1930s or early 1940s, the name was applied to all the lenses made by Tōkyō Kōgaku with advanced specifications, as opposed to the Toko or State brands, used for three-element lenses. In 1955, the names Toko and Simlar were replaced by the single brand name Topcor.
The State agnastimat is determined as the frist lens which apeared on the market. It appears as thought that as the compagny developed it adopted Toko and Simlar as bran names, later to be replaced with Topcor.