Hi milford, Happy Hogmanay,
The name Rotarex looks a lot like the Vortex that was made here in America around the same time. I'll try to research that for you later today, but I believe that was also made by Apex. This raises a huge red flag, but in a good way. One of the key inventors was James B. Kirby who was designing washing machines. You said circa 1920 - 1930, that was the same time Jim Kirby was experimenting with several ideas for Apex, Scott/Fetzer, and Vital Rand to name only a few, and yes, Jim did market to Canada and England. As I said, I'll have to research this for you, but I think you have a very early Kirby design.
Alex Taber.