Taken with a Koroll 24 camera in week 132 of my 52 film cameras in 52 weeks project:
As the name suggests, this model manages to squeeze 24 exposures out of a roll of 120 film, by using a mask to make the image size 3cm x 4cm. The edges of the film are wasted, but by using the "12 frame" backing paper markings twice, 24 exposures are made.
I removed the mask, so the full width of the film is exposed, and the frames overlap, but if a full frame is desired, the film can simply be advanced twice.
The film was expired Fuji Velvia ISO100 slide film, which I cross processed in Tetenal C41 chemistry.