and I never encountered any legacy 50Hz appliances.It's very unlikely that many appliances from that era would have been dependent on the mains frequency. As far as the appliance would be concerned, as long as the mains was close enough to the 'standard' voltage, pretty much any mains frequency would work normally.
About the only thing I was able to think of from that era which would have been mains-frequency dependent was electric wall-clocks.
And, as the article mentioned, turntables. Though electric turntables were fairly rare in my experience till about the early 50s, clockwork being the norm. Remember those wind-up gramophones and the brittle 78 rpm shellac records?
Both of those would have a very-high priority to be replaced as quickly as possible when the local mains frequency was altered.