Judging by the pencil guide lines still visible on the back for screw holes and the hand written indicators for the terminals and overlapped hospital corners on the grille fabric I think it's a safe bet that these are home made. Also the screws across the top aren't centered evenly from the corners which indicates a lack of thorough planning. It doesn't look like the sides/top/bottom are miter joints either - just the top and bottom butted into the sides. I'd further a guess that the masking tape is holding the grilles on because they weren't completed with a proper fastening set up to the cabs. That or there is no grilles the fabric is just stretched across the front because the maker never made the grilles. Have you looked inside at the drivers for names? Wouldn't mind a pic of the back of the grille and the inside of the cab_
My guess would be homebrew as well. Judging by the nice looking room in the back ground, the 1900 and what appears to be a decent quality cab they just might be something worthwhile
The fact that the top of grill wraps around the sides like a K-horn is very intriguing. Maybe there's a nice compression driver/horn combo hiding in there.
The fact that the top of grill wraps around the sides like a K-horn is very intriguing. Maybe there's a nice compression driver/horn combo hiding in there.