An 803 vacuum tube (pentode), made in 1942 for the U.S. Navy by <a href="https://en.wikipedia.org/wiki/Westinghouse" class="extiw" title="w:Westinghouse">Westinghouse</a>. This tube was intended for radio transmitters, and can produce an RF output of 200 W at 2000 V of plate voltage. The filament alone draws 50W! (5 A at 10 V)
<a href="//www.flickr.com/people/36473423@N02" class="extiw" title="flickruser:36473423@N02">Nick Ames</a>
CC BY-SA 2.0
<a href="//commons.wikimedia.org/wiki/Flickr" class="mw-redirect" title="Flickr">Flickr</a>: <a rel="nofollow" class="external text" href="https://www.flickr.com/photos/36473423@N02/4082408398">803 Vacuum Tube</a>