It's no RCA, but this theremin on eBay does look like it comes from an era gone by. I don't know enough about the design to be able to tell which model it is, but it definitely appears to be custom built - likely from a magazine article. Too bad the seller didn't post links to any sound clips, and the auction doesn't mention if it works or not. Still, this could be a nice theremin to add to your collection!
