Sometimes referred to as the "Italian Enigma," the OMI  Nistri was a 5 rotor cipher machine produced and sold by the  Italian firm Ottico Meccanica Italiana (OMI) in Rome in the 1939 to  1940 time frame. Ottica Meccanica Italiana (OMI) was an Italian company producing photogrammetric instruments and was founded in Rome in 1926 by Umberto Nistri (1895 - 1962) . From 1962 onwards, Raffaello Nistri (1920-1981), son of Umberto, was president of the company. Since the 1980s the company has been part of a part of the Agusta group.

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Exterior view. The printwheel has two parallel sets of the same alphabet and the printed output / paper-tape passes over a circular blade. This results in two wo copies of each message.
With cover off. Note that there is no letter 'W' in the Italian language. The 'W' key is therefore  used as a space character.  The CX-52 (which was sold all over the world) can be adjusted to use A, J, K, W, X or Z for spacing. Presumably, any given CX-52 customer would choose the least-used one of those letters based on their native language.
Closeup of the voltage selector switch. The two red bakelite knobs near the motor worm gear provide the means to switch between AC and DC power. There is a large bar that swings between the two contacts and can be locked down.  Power input is 120 to 260 VAC,  42 to  50 Hz or 12 VDC. 
Right side 
Left side
Closeup of motor. The red and green wires hanging out of the case are not original. They are providing a temporary power connection. 
All photos in this table by John Alexander 
Closeup of rotor order.
Rotor III - front view. This was typical for rotors I, II and IV.
Rotor III - rear view. This was typical for rotors I, II and IV.
Reflector rotor. It was a moving rotor. - front view.
Reflector rotor - rear view.
All photos in this table by John Alexander

Contributors and Credits:

1) John Alexander <jalex_uk(at)>

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July 13/09