|Perkeo 3x4 w/Embezet shutter image by David Edwards (Image rights)|
The 3x4cm size is the half size of 127 film's 4x6.5cm. As it took 16 exposures to the full size and made the camera smaller, many manufactures made this size camera. The Perkeo means a pigmy. (No, it doesn't. The name comes from Clemens Pankert, see http://en.wikipedia.org/wiki/Perkeo_of_Heidelberg respectively http://de.wikipedia.org/wiki/Perkeo. The word for a pigmy in German is Pygmäe.)
The lenses are Heliar 4,5/3,5cm or Skopar 55mm F3.5 and shutters are Embezet or Compur. Focusing knob on ths body, focusing is possible while camera is open or closed; frame finder: round optical finder or square simple frame finder; self-timer; self erecting bellows; camera leg (optional); depth of field table on front.