This is a United Electron 833A vacuum tube marked Made in Germany. The 833A vacuum tubes are made for medium power oscillators and Class B or C amplifiers. Sometimes called a "cookie jar" tube because of its large size (about 4-5/8 inches in diameter and almost 9 inches end-to-end), They are often used in pairs to produce 1000 watts of power for a small AM radio station. Some hobbyists have used them to power a vacuum tube Tesla Coil. Working or not, these are spectacular and rare display pieces for collectors and radio aficionados. We cannot test these, so we don't know if it is still functional.