Could be an Issmayer ( I am no expert on them tho) but for some silly reason I cannot back up with anything but gut, Adolph Schuhmann comes to mind , there is little info out there but a lot of his locos, came with that extended lower sides ... Bub kinda did it on a few models , but nothing like your example that I have seen Steve...
OHHHHKAAYYYY Searching using my best google-foo I have come up with a match I think?
Providing this ebay seller knows what hes got , it IS a Bub (you learn something new every day , maybe? lol)
https://www.ebay.de/itm/Bub-KB...d:g:cdoAAOSw~NdcuucV
I would say the black on yours is someones handywork ? Unless Bub was clearing out some Stealth Versions