[Arran]

There is too much missing to repair with epoxy at the rear of that 91B cabinet, it looks like a 1/2 or more has been gnawed off, several inches or more up the back, at only 1/8'' thick, if you try to fill that much area with epoxy it will chip off in short order. It could be patched with veneer, which in this case runs from back to front on the outside, and possibly on the inside, the middle layer will probably run 90 degrees to the other two. It may be easier just making, or buying a replacement from Steve, since it's a cathedral model it's collectable enough to do it right.
  As from why that Stewart Warner cabinet was painted, the old finish went bad, they may have stripped it, and found that the top layer of veneer was sanded through at the factory. This used to happen from time to time, I have had a few Electrohome sets built for Eatons under the Viking name, one I stripped and found it on the front, on another I can see it under the shaded finish since the grain does not look right. Since they were marketed as private label sets, and lower end ones at that, they probably let them slip through since they knew that the whole cabinet was going to be covered in a light walnut tinted lacquer, and nobody would really notice. Painting a cabinet white I don't really find that surprising, but why some would paint them weird colours, with that ugly antiqued effect finish, or with speckle stone paint I have to wonder about.
Regards
Arran