The only problem with it being a lamp holder, is it would be in the inverted position facing downwards, eliminating the shadow from the base of the bulb and the holder, not facing upwards. Also, if there had beem a twin flex connected through the pipe running down to and past the hot iron, how would one heat the iron without damaging the flex, remembering that in those days, any electrical cable utilised in the household would have been insulated with a rubber coating.
Regards
Malky