Eric,
I remember as a kid growing up in Toronto that they changed from 25Hz to 60 Hz sometime in the early 60's before 1964. The power company replaced the compressor in my parent's fridge and that of my grandparents during that conversion. I guess they did everyone's. That must have cost them a fortune!
Unlike electric motors though 25 Hz power transformers if anything actually run better on 60 Hz.
That huge 25 cycle transformer sure looks strange in that 19A11. As for pre-war design shelved? I don't subscribe to his theory.
Some of my 40's Admirals have the 25 cycle power xfmers. There will be extra supply filtering and circuit changes in the sync detector so that the set's vertical oscillator won't be fooled by 25 Hz mains.
Can you imagine UPS shipping that set? One drop kick and that heavy iron would launch right through the bakelite case.
Rob