[Ron Ramirez]

It isn't just higher line voltages (although they are a contributing factor).

Bear in mind that the original measurements as made by Philco technicians and printed in their Service Bulletins not only assumed a line voltage of 110 or 115 volts, but they also used voltmeters with an input impedance of 1000 ohms per volt. These old meters tended to load the circuit under test, making the readings appear lower than they actually were. But it was all that they had at the time, so that is what they used.

Today's digital multimeters have an input impedance typically in the megohms per volt, which does not place as much of a load upon the circuit under test. As a results, voltage measurements will be higher than they will be with an old meter with an input impedance of 1000 ohms/volt.