This is one of two derailleurs in this collection that :
This example has a faithfully, but rather imprecisely, copied bronze parallelogram matched with a steel pulley cage. Lashings of chrome have been enthusiastically ladled over the parallelogram and the outer pulley cage plate, but not the inner pulley cage plate. The design of the inner pulley cage plate is also completely unlike anything that Campagnolo ever let anywhere near a Gran Sport. It is slightly strange that the maker took so much trouble to patiently copy so many features of a Gran Sport - and then lost concentration and fitted their own design of inner pulley cage plate. Finally, it weighs a stonking 340g - a real Gran Sport comes in at around 300g.
Although it looks badly finished and crude, I would comment that this derailleur feels solid in the hand and operates smoothly without any looseness in its joints or pivots. It is certainly a usable device for changing gears.
I obtained this derailleur from Poland, and have been assured that it was made in that country, probably in the 1960s. This would make a certain sense, as, at a time when the Berlin Wall had just been constructed, it was probably relatively difficult to import frivolous western luxury goods into Poland.
Unfortunately, I have not found any real, hard, evidence for who made it or when or where it was manufactured.