Phasing was such a problem to get right that IBM just started putting a phasing jumper in the machines that cared (3p motors) and the ones that might self destruct had phase rotation detectors so they wouldn't even power up if it was wrong. (disk drives that didn't "unload" the heads)
Prior to that we were swapping the phasing in our disconnect box (or some other convenient place). It got so out of hand that there probably wasn't one machine in the country that had all the wires on the lugs they shipped on.
Sometimes we had machines that had it swapped a couple different places in a single machine.
Part of the problem was, do you look for clockwise rotation on the face of the plug or the face of the receptacle? IBM couldn't make up their mind about the from one plant to another so a brand new tape drive from Boulder would be phased differently than a disk drive from San Jose
We always had one particular motor we would look at to see if it was going the right way.
