Those slate panels are becoming more and more scarce. I was in an elevator tower the other day that had the elevator controls and contactors mounted on a slate panel for the 1927 Otis elevator.
i remember reading about 2 phase systems and learning a little in school about them but never seen them in the field yet. anyone here ever see an old 2 phase system? i would love to get my hands on some f that antique electrical parts. looks like a piece of art work and not a piece of electrical equipment