Testing quad provided by Katanga. Thanks!
General-purpose 12 gear bottom bracket gearbox. 600 % range with evenly spaced gear ratios, chain ratio is usually close to 1/1, chainring has 24 or 30 teeth. Lubrication by oil bath, oil change is recommended after 1 year or 10000 km. Weight slightly over 2 kg. C1 is the lower end series (6, 9 and 12 gear versions exist), P1 is high end (9, 12 and 18 gears).
Shifter is of twist grip type with two cables, similar to Rohloff, but accuracy and feel is more like Sturmey and Archer: it works well, but it's no bombproof engineering miracle, misshifts are possible if you are not careful. But the quad was a prototype test-ridden by many potential customers and I don't know anything about its level of adjustment or maintenance, so take this information with a grain of salt. The photographed shifting handle (originally throttle from a moped) is a nonstandard modification for vertical handlebars, normal shifters are as short as usual.
Chainring runs on a freewheel, so forget about backpedal brake in rear wheel. On the other hand, you are free to kludge things like motor on the chain return run. Second freewheel is necessary in the wheel for safety reasons: you don't want an unstoppable chain spinning next to your ankle on a high speed descent.
The gearbox is only sold to frame manufacturers who can make the special fixture with its tight tolerances and the right stiffness. Mounting the not-self-supporting shell to anything else will ruin the device quickly. Your only choice is to buy a whole bike with a special frame, or swap the pedal boom of a recumbent for a special one.
I will probably never gather any more experience with this gearbox. If you want to share yours, feel free to do so.