Happy New Year!
can you put a year on that example?
It's most likely out of a older model Fender Super Reverb or Bassman According to http://www.svvintageamps.com/dating.phpIf it came out of a blackface ampThe code 606-431 indicates it was made by Schumacher (606), manufactured in 1964 (4) in the 31nd week (31)If it came out of a silverface amp it could be 1974.
the more laps you use, the more of a gap the transformer sees.so on some of the nickel stuff, the lap 5, or lap 6 so the do not saturate. most mains stuff is lap 3.
i will scan some pages on coil geometry and post them, with this new camera it will actually be readable.
wax, varnish, and paper insulation can all interact to form a dialectic between the layers.plus the copper wire has a coating, and air, so you have a cap with 5 dialectics, this means the fastest way to model it is to do experiments, but all that has been done,
so just copy what the best transformers do and avoid re inventing the wheel.
shugg wrote a 500 page book on insulation, if you want to fall asleep at night, read that book.