Optochrom filters often appear on eBay. In an online forum somebody stated that the company which made these filters (in the 1930s) was Japanese and not related to the Optochrom company which made the tank in Germany. Wrong!

I found an advertisement in the 1937 British Journal Photographic Almanac for Optochrom glass filters showing they were made by Optochrom GMBH of Augsburg. The British agent was Sands, Hunter and Co:

Optochrom Filter

So, the filters were not Japanese.

I then found the German Patent for the Automat tank (Tageslichtentwicklungsdose, daylight developing tank) granted the Optochrom on 16 November 1936. Here is part of the front page:

Screen Shot 2013-12-24 at 10.51.50

and here is the drawing from the patent:

Screen Shot 2013-12-24 at 10.52.23

Interestingly, there was, in the 1930s, a Japanese company called Optochrom. The history is in Camerapedia under the name of Kigawa. Whether the Japanese company was the agent for Optochrom, Germany, I do not know.