This is an instruction leaflet for Constrictor’s innovative parallelogram derailleur - which famously appeared many years before Tullio Campagnolo supposedly invented the parallelogram format.
It is hard to know exactly what call this derailleur. The headline of the leaflet is ‘Constrictor Derailleur’, the second paragrah of text refers to ‘the new Constrictor Osgear derailleur’ and the spares list is for the ‘Constrictor Conloy Derailleur’. I am going to settle for Constrictor Derailleur.
I rather admire the look of this leaflet - particularly the cover picture which is finely realised.