If that's a Nuovo Record rear derailer, the frame must have been modified to accept it. It involves much more than tapping the derailer mount. The hanger has to be reshaped to give clearance and form a stop. It destroys the collector value of the frame. Collectors won't consider the replacement of the French parts with Italian to be an upgrade, either. It doesn't effect its value as a rider, though. My PX10 also has all Italian components because that's the way I want it.