Yes, I am always amazed at what people think old junk is worth. Not that I don't think that it is really cool, but vintage compressors have a very limited resale market. I've scrapped out a few of my grandfathers' old compressors that parts couldn't be sourced for.
But you never know with stuff, on a lark I have brought broken junk to a swap meet that I was going to scrap and to my surprise people bought a lot of it (for cheap, as my goal was to not go home with anything).
Thanks for posting this, I have never seen a 4-cylinder version!