I incorrectly stated in the previous post that most series 1950's sets had polarized interlocks/plugs.
DUH-me on that. Neither of my 1956 metal-case 14" BW sets have them and neither does my 1958 Philco seventeener. My 1963 Westinghouse attache 19 BW TV did have a polarized plug. Being an electrical switchgear manufacturer, Westinghouse took safety a bit further than others. This was probably optional for a long time before UL required it. Must do some research on that
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I got zapped quite a bit by 120 in the old days and fortunately I recoil as opposed to clenching. A Sunbeam mixer shocked me and trip the GFCI simultaneously one time. I put a grounded cord on it after that.
GFCI receptacles are OSHA required at construction sites due in part to the fact some tradesmen use older, metal case power tools where the ground pins were routinely cut off. I see guys working around puddles on concrete before a roof is on.
GFCI is simply a current transformer surrounding both line and neutral conductors. It does not include the ground conductor, nor does it require one to operate. If ANY current is going out on the line and not returning on the neutral, the differential current (usually only 6.8 mA) is detected and trips the unit open. There have been improvements over the last 30 years so they don't false-trip so much, such as from a static arc, etc.