Another perfect example is the sheet-beam deflection tube, like the 7360. Those probably made the best mixer, converter and detector devices ever developed. They were sensitive and had very linear characteristics, producing minimal spurious intermodulation products, although 60~ a.c. hum could be a problem from the magnetic fields produced by the filament and nearby transformers. Eclipsed by solid state technology just as they were getting off the ground, and now hard to find and probably way too expensive for the typical homebrew project. Also, the subminiature tubes that began to appear after WWII, some with wire pins arranged in a circle to fit into a socket, while others had longer wire leads intended to be soldered in. There are still loads of those out there crammed away in junkboxes and no doubt many have been thrown away. One problem is that characteristics data on those tubes was always difficult to impossible to find and many were tossed because no-one could find information on them, although that has become more widely available with the advent of the internet. Those would likely have soon developed into the standard variety of tubes, just as 7- and 9- pin miniatures replaced octals, which in turn had replaced the older glass tubes with 4, 5, 6 and 7 pin bases. Solid state technology emerged before that was able to happen.