[David]

Back in the day mains power could be very different than what we have today.  In the USA having 120 volt 60 hz was not everywhere in the country until 1980+or-. Growing up in Tampa I can recall my dad having trouble with the fuse box, if a fuse blew and you measured from the neutral to a ground got 60 volts!! Both wires had a fuse what we today would call hot an neutral. My dad had someone come out to look things over and he would have the panel changed but the power company had to install a new transformer on the pole. the old transformer was 120 volts only and each side of the plug was hot. If you measured either side to ground got 60 volts AC. The other houses on the block were still on the old transformer the last ones were changed my senior year in High School  1967. In 2010 was visting friends in OZ went to Philip Island for a stay at there summer house and was asked to look at the wiring what I found was both wires were hot 230 volts 50 Hz.  each side to ground was 115 volts 50Hz. House was built in 1947 no grounds in the outlets. There was a old tube radio at the house that was his aunts from when she lived in the house I did restore the radio for my friends and both wires were switched It was a Phillips. In 2017 I was gifted a signal corp generator made in 1954 model PE-75-AF was able to get the gas engine running  and the thing makes power has a 2 prone twist lock plug no ground. the TM states you run a ground wire from the gen set to your radio equipment. measuring from  either blade to ground is 60 volts blade to blade is 120 volts. Was able to find info on radio equipment used by the signal corp during this time frame and both wires are switched. Sorry about the long post