Finally starting to dig into my 1956 Packard Bell and the yoke has this white junk on it. Is it some sort of corrosion and how should I treat it?

Looks like "knob fungus" some plastics like to form it. It's harmless electrically, and on some plastics it can be cleaned safely with a soak in windex (some plastics are harmed by it though)...Don't soak the coils.

Yoke cover plastic of the 50's and early 60's has a tendency to become brittle and disintegrate so be careful with it, and be wary that this could be a manifestation of the beginnings of that.

Interesting. Thank you!

Could be an oxide of magnesium, zinc, or tin... or some mix....
battery activity of 2 metals in contact with each other...

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