Toronto. In 1951, Leitz offered a Universal Focussing Bellows (Bellows I). This bellows worked with the 13.5cm lens head and Visoflex mirror box to make photographs from infinity down to 1:1. A 5cm lens head and the focoslide focussed from about 3 feet down to about 2.5x magnification.
The bellows offers scales for both lenses to permit rapid settings. Many other manufacturers also made bellows. The design goes back to the early days of photography when a bellows was used to correctly set the distance between the lens and sensitive media to correctly focus the desired subject.
Leitz later replaced this bellows by the Bellows II which brought a special 65mm lens (or longer) into focus at infinity. Shorter focal length lens heads can be used as well for copy work. The scales were for a 9cm lens head. Both versions of the bellows eliminate the need for extension tubes and their discrete steps in focussing.