This little jewel was sold in several electronic supply houses in the mid 60's. It was a crystal microphone with two elements and a switch giving it both cardioid and bi-directional. I bought my first one for about $10.00 It was designed in the style of the RCA 77's, just much smaller (less than 6 inches tall) and with no where near the sound quality. Yet they look good, and have made their way into advertising and movie shots. Several years ago I saw one in an antique store for over $125.00