That B&W set with the tubes, is it a "hot chassis" design? If it is, I wonder how they dropped the 220V mains to run the heaters. Or did the heaters add up to 220V?
You may be amused to see that we in America had outlets that would fit your plugs. It was an early proposed grounded outlet, before someone figured out that just adding an extra pin to the existing 2 pin pattern we had made more sense. This dated back to the early 50's.
This one, in my mom's house, is fed the two 120V lines most all American houses are fed, to provide 240VAC centertap grounded. At 60Hz, though.