One last thought on external power supplies in BA gear...

Back when American manufacturers dominated the amateur radio market, most ham
gear (except big transmitters) was made to work from USA standard 120V 60 Hz
"house current". Much of the rest of the world, however, ran on 240 V 50 Hz.
Some parts of the world (as close as Canada) had 25 Hz power.

Power supplies that could handle other voltages and frequencies were larger,
heavier and cost more than those designed for 120V 60 Hz only. The cost saving
increases as the power level rises, so it made economic sense in many cases to
offer power supplies meant for 120 V 60 Hz as the standard, with "export model"
supplies available at higher cost.

73 de Jim, N2EY