Here's another British item from the past, the "FITALL PLUG":
The little black lever at the bottom moves a plastic "template" to cover and uncover various retractable pins. Move it into its central position, turn the plug over so that gravity comes into play, and out pop three rectangular pins. Turn them 90 degrees to lock them into place, and you have a plug to fit a 13-amp BS1363 outlet:
Move the lever to right, and you get round pins which when screwed out to lock them will fit a 5-amp BS546 outlet:
Move to the left, and you can operate from a 15-amp BS546 outlet:
Back in the 1960s all three systems were still in widespread use, so this plug was intended for portable equipment which might be used in a variety of different locations. The alternative was to carry an assortment of adapters.
[This message has been edited by pauluk (edited 06-17-2003).]