These Olympus medium format cameras are true oldies, and you will not find many of them which are available for sale or on auction sites. These cameras were manufactured from 1936 till 1952 when the medium format was the camera of the day. Production ceased when Olympus made the change to push into the then-new 35mm film format, which the company had already started in 1948 with the Olympus 35-I model.
For the record, Olympus was first known as K.K. Takachiho Seisakusho (Takachiho Works Co., Ltd.), a manufacturer of microscopes and thermometers, which was established and started production in 1920. As an 'approved company' supplying microscopes to the Navy, Olympus also supplies an apparatus to take pictures with a microscope, a ground glass dark box with a prism, and a basic shutter mechanism.
The beginning of Olympus as a camera manufacturer started in 1934 with the first serially produced lens, a four-element Zuiko 75mm f/4.5. The lens was fitted to a body from the Semi-Proud, branded, and commercialized as the Semi-Olympus I.
Semi-Olympus I (1936)
Hold the camera horizontally, and you will find the advance knob at the bottom right with film advance controlled by red windows. The four-element Zuiko 75mm f/4.5 engraved Takatiho Tokyo Zuiko 1:4.5 f=75mm. No.1xxx focuses on turning the front element.
The Semi-Olympus I with the Compur shutter version comes with a T, B, 1–250 speeds, and has a self-timer and a thread to attach a cable release, while the latter with Rulex shutter comes with a 1–200, B, T speeds, a thread for a cable release but no self-timer.
Semi-Olympus II (1938)
The form factor of the Semi-Olympus II is that of a horizontal folding camera, constructed with a pressed sheet-metal body with a side-opening design. It is fitted with the same Zuiko 75mm f/4.5 lens as on the previous Semi Olympus.
Olympus Six (1940)
There are strap lugs at both ends of the top plate now, which replaces the leather handle of the previous model, and no accessory shoe. With this camera, Olympus established the basic format for subsequent Six-series cameras. Lenses mounted on the Olympus Six are the four elements Zuiko 75mm f/4.5 (same as on the Semi Olympus and Semi Olympus II) and the new Zuiko 75mm f/3.5.
Olympus Chrome Six I (1948)
All Olympus Chrome Six models have front-cell focusing 75mm Zuiko lenses, with either f/3.5 or f/2.8 aperture, and Copal shutter except for some very early cameras. Olympus Chrome Six I, II, and III have a flat all-chrome top plate, a tubular finder with parallax indications, and translucent blue strips showing the field of view for 4.5 × 6 cm exposures.
Olympus Chrome Six IIIA (1951)
Olympus Chrome Six RIIA (1955)
The body design was also innovative, the film winder was changed to a lever on the reverse of the body, and an automatic winder stop system was added. This camera, and the V, which had no range finder, were the last models in the Six series.
Olympus Flex I (1952)
The shutter is a Seikosha-Rapid (B, 1–400), in #0 size. Both lenses are 75mm f/2.8 with bayonet filter attachments. The taking lens is a six-element F.Zuiko F.C. and the viewing lens is a Zuiko F.C. Though modeled on the Rollei Flex, the camera incorporated numerous unique Olympus features.