I sure remember the DT-48 series from the 1970's, since I bought 3 sets including the 48S with the round audiometric cushions. I don't specifically remember a DT-48 'A' version, but then again, there were no letters following the black versions either, like the 25 and 200 ohm versions. And in all of the literature and photos I saw back then, there were no red earcups either. But since we didn't have the Internet, I could have missed something.