The following information is taken from Dr. Ron Dutcher, Kamakura Pens, listing for this particular pen:
Here we have a very interesting 1930's Mitaka Fountain Pen.
The cap and barrel are made of vulcanized hard rubber which a maki-e artist coated in rich black urushi lacquer.
What is really nice about this pen is the springy flex nib. It has the Big V vent, which allows the pen with greater flexibility. The nib is ideal for copperplate style round hand calligraphy or it is just a fun pen to write with if you like to add a little flourish to your words.
The Mitaka Pen Company is one of the more interesting of the obscure Japanese pen makers. Mitaka is a small city just outside of Tokyo. The city is situated upon a pleateau, and is known for its breathtaking sunsets with Mount Fuji on the horizon. The intriguing beauty has lured many artists,poets and writers to live in the area.
One of the most famous of these writers is Dazai Osamu. In his novels he frequently wrote about the Mitaka sunsets. One of his books was even named "Shayo" which, translates as "Sunset" In the late 1930's when this pen was made Dazai was one of the most popular Japanese novelists. It is clear that the pen maker chose this logo to allude to Dazai, and advertise that this pen was made for writers and authors.
The only other reference to the Mitaka Fountain Pen Company, was a mention in a thread on the Fountain Pen Network, that the company produced lower quality pens in the 1950s. Well, that may be how they ended their company life, but this is a nice quality pen.
Click on image to view larger version:
I have been asked how this shut off system works, so I'm adding this information to this post. There is a review on this pen on the Fountain Pen Network by member troglokev. He drew a very nice diagram of how the sytem works: