Topic: 3 wire heater motors

[Oz390]

Picked up a Ok condition heater box.  Has a 3 wire setup, which I think is a very early style.  Door opens to the side, and the clips on the box are far thinner than the ones I am used to seeing on the 67/68's I usually work on...

Y4AK ink stamp.  Some broken fiberglass repaired on the face by the outlets from the core, can't be seen when installed.

Hard to find item?  Worth hanging onto and restoring?  Dates for when this would have gone out of use and the changeover to the two wire style happened?

[midlife]

I believe the changeover date is February, 1965.