An article appeared in the  Pathescope Gazette of June-July 1956 announcing : "It is with very great pleasure that Pathescope bring 9.5mm to the forefront with WIDESCREEN especially prepared for home viewing in most pleasing dimensions"

This was to be achieved by perforating 9.5mm with a double set of perforations and filming horizontally then splitting the film into two. "This new double peforated film when the full area is exposed will be known as DUPLEX, and MONOPLEX is the name given to it after slitting.
 

The new LIDO cinecamera was specially adapted to carry the new film. The camera was operated horizontally and designed such that it fitted easily into the hand for filming either horizontally (WIDESCREEN) or vertically (full frame
format).
 
 

The MONACO projector was designed with three gates to permit the projection of of the three types of film DUPLEX, MONOPLEX and the CLASSIC 9.5mm. When showing Classic films the spool arms and rels are vertical. To project MONOPLEX the film the front assembly of the projector which hods the lenses, spool arms and spools is rotated 90 degrees, the film passing through the projector horizontally. New toothless sprockets were designed so they could accommodate either 4.75mm or 9.5mm film.

The setting up of the projector was quite complex and the operator had to be very careful to retract the claw before rotating the front mechanism otherwise the claw could be snapped off! A detailed Instruction Book outlined all the necessary steps to convert the machine from 4.75mm operation to classic 9.5mm operation. One can't help being drawn to the conclusion that the complexity of this machine was rather advanced for the average home movie buff.

This innovative format was very short-lived. Apart from an enticing advertisement for the LIDO Duplex Cinecamera and an article about filming in widescreen in the October-November 1956 Pathe Gazette,   the format quitely faded away after a final mention in the Dec 1956-Jan 1957 Pathescope Gazette:

"Many will have seen and read notices of new equipment which has been introduced during the year, and Pathéscope add yet another camera to their list of equipment available to the enthusiasy, by announcing that a Classic version of the Lido Duplex Cinecamera is now available. This answers the needs of those  amateurs, who for long, have been asking for a single speed 9.5mm spool loading cinecamera with a type C lens.
Thus 1956 has passed behind us and if we remember that the cinecamera is the finest instrument for recording the past for the future, this next year will hold greater promise for all of us."
 

No doubt the cost of developing such a complex projector system had added to the failing returns of Pathescope's activities which were to cease altogether just four years later.