[morzh]

The best way is simply to measure it with calipers or a micrometer.

Wach your direction, count turns, and try to replicate geometry as close as possible, meaning lengtsh of windings and location of them on the bobbin / relative to each other.
This way you duplicate both the inductive coupling and inductances.

Take photos / make sketches.
If just one winding is open, and the other looks good, no green stuff etc, rewind just one.
There is something about baking old bobbins....I don't but maybe there is something good in doing it.