[Winky Dink]

The service manual specifies 60-cycle and 30-cycle models with slight differences in the power supplies. I've seen several other radios of that era that offered 60- and 25-cycle models. The cities (and even small towns) in my area--Southern Idaho--all had their own commercial power companies, so I guess they chose whichever worked best for them.
I didn't realize that a radio could use either type of current with, at most, minor modifications to achieve the best performance.