The product is a vintage Eimac electron vacuum tube with the model number 3-400Z-EIMAC(?). The type and model is rubbed off so the model is just a guess as this was an estate sale find. This particular tube has 5 pins and is untested and I have no way to test it so selling for parts. It may work as intended. Vacuum tubes were commonly used in vintage audio and video equipment for amplification or signal modulation purposes. Eimac is a reputable brand known for producing high-quality vacuum tubes for a variety of electronic applications.