Any industry insiders out there?
Curious to know the change from the early 1971 17M6 45222A VS the next generation 1972-on 17M6 45220A. It is likely to be small and only internal change of one or a few small components.
They are both primary 1.9 ohms which of course is of no concern, since that is a DC characteristic and coil are AC devices.
I dismantled a 45220A to have a peak, as it was with a typical crushed case, but also a possible crash damage that compromised the oil tight seal.