[Arran]

I performed a little research on this model, which believe it or not is posted on Nostalgia Air, a source that usaully has large gaps in it's collection of Canadian radio schematics. There is some good news, if you could call it that, the sub chassis only contains the power supply to the radio, the rectifier tube, the filter condensers, the power transformer, and a pair of filter chokes.

http://www.nostalgiaair.org/PagesByModel...029191.pdf

So my second guess was right, someone likely removed the power supply chassis because something went wrong with it, either that or it belonged to a Ham or some other experimenter that decided to use it to power something else. Building a power supply to produce the correct output voltages isn't a problem, but making an exact replica of the original would be a problem since horizontally mounted transformers of that size aren't exactly off the shelf items anymore, most are vertical mount now.
I don't know if it helps but apparently the same pair of chassis were used in three different models, according to the data sheet, a Rogers 10-12, a Rogers 10-120, and a Majestic "Normandie" (Canadian Majsetic of Course). It would be a difficult item to find but at least we know that the workings in this set was not a one off.
Regards
Arran