The Patent Etui are extra-slim folding plate cameras, they were manufactured in two sizes 9×12cm and 6.5×9cm by KW Kamera Werkstätten Guthe & Thorsch of Dresden between 1920 and 1938. Although originally designed for glass plates both sizes also accept Rada or Rollex 120 6×9 roll film backs as well as film packs (long discontinued).

The 9×12 Patent Etui weighs 815g, and was considerably smaller than most of its German competitors. In comparison a 4×5in Crown Graphic weighs 2.4kg. The cameras were often fitted with an f/4.5 135mm Zeiss Tessar initially in a dial-set Compur, and after 1931 in the new rim-set Compur. They were also available with an f/4.5 150mm Tessar.

The 6.5×9 cameras were usually fitted with an f/4.5 105mm Zeiss Tessar, again in a dial-set Compur, and later in the new rim-set Compur. They were also available with an f/4.5 120mm Tessar. Two budget triplet lenses the f/4.5 & f/6.3 105mm Meyer Gorlitz Anastigmatic Trioplan were also available, the f/4.5 in a Compur shutter and the f/6.3 in a 3 speed Vario shutter.

A few Patent Etui's were also sold with lenses from a variety of other manufacturers, and there were also some variations of the two basic models, including one with no focus rack adjustment instead having a Schneider Radionar with front cell focussing, and an Ibsor shutter. Not all cameras were fitted with the sports finder.

A Japanese copy of the 6.5×9 model, called the Prince Peerless, was made from 1934.