Tom Purvis, a renowned artist, and Alfred C. Mayo founded Purma Cameras Ltd. in 1935. David Brock of Brock Fireworks gave financial help to launch the company in London. Their office was at Brock House, Langham St, London W1.

The cameras of the Purma brand were 127 roll film viewfinder cameras with innovative gravity controlled shutters, based on the company’s patents of 1935 and 1936, designed by founder A.C. Mayo. Purma cameras and accessories were sold by R. F. Hunter of London.

The most common, the Purma Special was made almost entirely of Bakelite, apart from the glass lens, plastic viewfinder optics and shutter & spring mechanisms. Styling was apparently due to Raymond Loewy’s London Office.

There were several interesting features;

The focal plane is curved, with a solid metal, curved focal-plane shutter with three speeds, controlled by a weight, which varied the slit-width. The shutter is cocked using a pear-shaped lever on the top edge, above the lens; the slit width/shutter speed depends on which way up the camera is held. Horizontal gives medium speed, vertical with winding knob down gives slow, and vertical, knob up, fast. See the Living Image site for photos of the shutter.
The lens is sprung to telescope out of the body when the screw-on lens cap is removed. Capping (and so collapsing) the lens locks the shutter release – which, unusually, is on the photographer’s left.
the ever-ready case opens upwards from underneath the lens, unlike most cases, which open forward from the back.
The Purma is said to be the first camera to have plastic optics, although this is in the viewfinder only.

Models

There were three models marketed:

• Purma Speed, introduced 1936; enamelled metal/chrome body
• Purma Special, introduced 1937; all Bakelite body (this model)
• Purma Plus, introduced 1951, costing £12-12-0 and lasting until ~1959; aluminium body

Another model, the SAMA, stayed in prototype status despite Purma’s 1952 patent on it.

The Purma Speed was a metal-bodied camera with a six-speed shutter, 1/25-1/200 and a flip-up viewfinder[1].
Specifications

Country of Origin: England
In production: 1936-1959 (suspended during World War II)
Shutter: curved focal-plane gravity controlled, 3-speeds, Slow: 1/25, Medium: 1/150, Fast: 1/450 (Special); 1/500 (Plus)
Lens: Purma Special – Beck Anastigmat, 2¼ inch (~57mm) f/6.3, collapsible
Purma Plus – Purma Anastigmat 55mm f/6.3 collapsible
Film: 127 roll film, sixteen 31mm (1¼inch) square exposures

Manufacturer : Purma
Produced : 1937
Classification : Miniature
Body Type : Extending Body
Construction : Bakelite
Film Type : 127
Film Width : 46mm
Image Size : 1¼ x 1¼
No. of Images : 12
Lens Type : Beck Anastigmat
Focal Length : 57mm
Focus Type : fixed
Focal Range : 10ft – Inf.
Aperture Type : Fixed
Apertures : f/6.3
Shutter Type : Variable Speed
Shutter Speeds : 1/25s, 1/150s, 1/450s
Size Open (w x h x d) : 153 x 72 x 70 mm
Size Closed (w x h x d) : 153 x 72 x 56 mm
Weight : 365g

Iconic: Famous, well-known and celebrated

Produced during the main Art Deco period.
Bakelite body with horizontal linear detailing.
Streamlined Moderne curvilinear body design.
Symmetrical body design.
Art Deco lettering on name plate.

Description

The design of this camera has been attributed to the London office of Raymond Loewy who was a Franco-American industrial design consultant for more than 200 companies, creating product designs for everything from cigarette packs and refrigerators, to cars, railway engines and spacecrafts. It surely shows the American Streamline Moderne influence.

It features fine ribbing on Bakelite and a tapering form, with a lens cap that conceals a telescoping lens. The shutter cannot be released until the cap is taken off and the lens extended.
Adjustable Shutter Slit
Adjustable Shutter Slit

The most unusual feature of this camera is the shutter, whose speed is controlled by gravity. As the photographs produced are square, the orientation of the camera does not matter. In the horizontal position, the camera has a medium shutter speed (1/150s). If the camera is turned clockwise to a vertical position, the slow speed is selected (1/50s). Turning it counterclockwise to a vertical position, the fast speed is selected (1/450s). The focal plane shutter is comprised of two metal plates that slide together across the curved film plane. As the camera is turned, the speed is varied by the position of brass cam/weight which changes the slit width. The mechanism acts with a spring, which in one vertical orientation acts against the weight to slow up the shutter and in the other vertical orientation acts with the weight to speed up the shutter. Ingenious!
Two film windows
Two Film Windows

Film advance indicated by two windows and is not coupled to shutter. Cameras were supplied with both red and green film advance windows. The green plastic windows were for panchromatic film and the red for orthochromatic. These could be interchanged by the user. The film is advanced until the image number is seen in the first red window, and for the next frame, the film is advanced until the same image number appears in the second window.

http://www.artdecocameras.com/cameras/purma/special/