Originally Posted by LarryC
So which is it?


RST is the incoming supply, UVW and XYZ are the motor connections.

See here: TOS lathe - manual Y Delta start switch

I remember looking through a catalog when I was a kid and seeing RST on a European phase-rotation tester and wondering what, if anything, the letters meant.

Other letters can be found to identify phases. Here in the U.K., for example, we often used RYB for red/yellow/blue, the standard phase colors (well, until recently!).