I managed to pick up a Zeiss 21cm f4.5 Tessar for near $15 including shipping. Mostly it was just really dusty, so a careful cleaning brought it back to nice condition. Some more cleaning on the barrel, and carefully applied white out made the aperture numbers readable again (down to f45). Seems to have an 18 blade aperture, unless my counting is off. Also seems to have some slight early effort at coating.
So far I have not tried it on my 4x5, mostly because I have not solved the lack of shutter. I picked up a nice Zeiss lens cap for nearly what the lens costs; a metal with felt lining slip on item. This is definitely heavier than many modern 210mm lenses, though a good lens board should hold it fine.
I think you can find many Tessar lenses on the used market at somewhat low prices. There are even later East German versions, though the front filter mounts are larger. My old version seems to be a 60mm filter mount, though I am not sure if the threading matches modern filters. If you have a focal plane shutter 4x5, then barrel lenses are an easy and cheap way to enjoy some old glass; otherwise you can just do longer exposures using a lens cap shutter.
Ciao!
Gordon