Oh yes ... one of my favorite topics. The original Voigtländer filters are simply wonderful, almost "over-engineered", and too beautiful to use. Just FYI in case you didn't know, the product code for this particular filter you are looking for is 308/37 (37 for the size, obviously), when scanning Ebay and similar sites it is sometimes easier to use this code as a search word. Other filters available were UV (317/xx), yellow G1 (301/xx), yellow G2 (302/xx), Syklight (325/xx) and Green (306/xx). Later filters are additionally marked with the letters "AR" which means they were coated ("Anti-Reflex"). If you cannot find the original filter, B+W and Agfa also made nice slip on filters in that size that might be easier to find (I use the G1 and Green filter from Voigtländer in 37mm and the orange one from B+W).