Hello

I saw this rear derailleur and shifter on local advertising site and had to buy it. Newer saw it before and didn't even know that it existed. Information on the web is quite scarce. Something on Disraeli gears and one thread on Tonton. Book "The dancing chain" has it on page 164.
Apparently it was invented in 50's and was a randonneur-type derailleur, capable shifting 6 cogs, 14-28 at the rear and had a chain wrap of 32. The shifter has an internal indexing plate with holes and a bearing ball that fits in the holes, thus indexing. The derailleur has a spiral shaped cutout on the axle that pivots the arm when shifting and by doing that it maintains constant chain tension.

Thats about all I know. Tell me more about it. What were the bikes originally equiped with it? Why it is rarely seen on 50's bikes?
And where should I attach the distal part of the cable? There is this bolt with the hole and looks like a small nail in the hole (last photo), I suppose this is the hole for cable?