[Chas]

I'll start start chipping away at it.

Do not "chip away", there is risk of mechanical damage that could obscure how it was made. Do look for poor connections to the errant coil winding, usually at the terminations. Besides, if it is an easy fix, the heat will drive off 90 years of moisture. A solvent such as mineral spirits will dissolve bees wax too.
Warm with a heat gun, bees wax only needs 140F or so... Look for poor connections at terminals, green spots are corrosion. Keep heat away if mineral spirits are used, fire danger. Spirit fumes will be carburized by heat gun, toxic, as well as dangerous

If intent is rewind, number of turns, wire size (type) is important. If there is a insulating layer between coils, that is celluloid and decays then corrodes the wire...

GL

Chas