this is a Nuvistor! it's a super-advanced vacuum tube that could have beaten the transistor.
in 1959, RCA took their tube-making expertise and made this micro miniature tube almost as small as a 1950s transistor
RCA developed all new equipment to make it. this machine seals a batch of Nuvistors automatically!
in the 1950s, tubes still had advantages over transistors -- they even lasted longer!
so how did they miniaturize the Nuvistor? time to cut one in half. check out the cross section!
i'd annotate my photo, but RCA published a really nice cutaway diagram, so i will show you that instead.
Nuvistors found their way into some high end applications but transistors surpassed them in a few years, and they just faded away.
fascinating to imagine an alternate reality where transistors never worked and people figured out how to miniaturize vacuum tubes, etching arrays of them on metal wafers and building computers. In fact, they could even have built the entire Internet using a series of tubes.
Introducing the Vacuum Transistor: A Device Made of Nothing

This curious mash-up of vacuum tube and MOSFET could one day replace traditional silicon

IEEE Spectrum