"I don't normally deal with delta either.. in my world, everything is WYE, or single-phase."
Yeah, deltas are a strange beast.
What I would do if I had a phase rotation meter:
1. Dig through my garage and find the pair of old 100 VA control xfmrs I have there.
2. Take them to the office of a friend who has 208Y/120 service.
3. Connect them between any two phases and neutral, with the secondaries connected open delta.
4. Connect the rotation meter to the secondary.
I think there are places where there are no delta secondaries at all. They seem to be unheard of in Europe, and I know of utilities in the US that refuse to connect new ones.
Here in my area, however, they remain quite common, although for years I worked on nothing but wye systems.
