Starting at 23 April 2022, all Obbligato capacitors come with a serial number which can be authenticated in the following official web page:
Where to find reasonably priced large value caps for the 300B WE connection? In the audio world there are not so many low cost high quality film caps. The ones commonly available are a little edgy sounding, adding a hiss, and a sing along with the music due to loose windings, voids, or poor quality films etc.
At 2004 Electronica Asia we met a rep from the 5th largest cap manufacturer in Asia. They had new production machinery from Italy, and Germany, in a spotlessly clean environment. The company was sympathetic to our audio cap issues. Samples were made with extra tight winding, no voids and thick coated aluminum film imported from Germany.