Or was this thing some totally homebuilt set by some nut ?

I'd call the builder a "skilled craftsman" but yes, that's what this appears to be.   The dial face and some other components were salvaged from the RCA receiver but it appears to use varactor-tuning with adjustments made by the array of pots that are switched for each band.  Looks to be 2009 construction from the date on the side,  nicely done.  I'd note that the ebay seller tacked on the "RCA" designation, the builder just borrowed the same model number.

73, Bob W9RAN