The RCA 885 Thyratron is an Argon filled three-element tube used in pulse and switching circuits. Roughly equivalent to a modern SCR, this device will momentarily short when triggered, allowing charge to dump for a high-energy pulse or to help restart the next cycle in a sweep circuit. This tube was designed for oscilloscope use and was purchased as a spare for my 1936 RCA 151. It was produced as part of the war effort. It's new old stock. Interesting thing about tubes is there's so many of them still available in the USA because we just made shitloads of them up until the 80s. This is in contract to most other countries where stock has become depleted.