This is the RCA KU3A ribbon microphone. To the best of my research, it is one of only 500 made and sold only to Hollywood studios. It has been described as the "best microphone in the world." It doesn't have a sparkling hi-end of modern microphones, but a beautiful mid-range with excellent off-axis rejection. The mic has an incredibly warm, musical proximity effect and sounds beautiful on vocals. This mic has hardly been used in the last 40+ years and is in very good condition. It has some scuff marks and normal surface scratches you would expect of a mic this vintage. It is in working condition, but might need professional servicing after all these years,; I don't know this; it sounded all right when I did a test recording.