I had a bad one in my /29 rogers set. It was potted in tar. I melted it apart outside in a pot of oil , boy that was a messy enterprise and probably not the best method of taking one apart 🙂 It had a lot of fine wire. guessing maybe 1000 turns but that is purely a guess. as I recall I measured it at .007" with my digital calipers. If that seems off it may be , It was was about 10 years ago.
I replaced it with a tiny by comparison replacement from AES. It did work, but I wondered about wheather using a more closely matched transformer would have improved the sound quality or something. Surely they wouldn’t use all that wire for no reason. I might possibly have the iron plates and perhaps even the spool somewhere if you want me to look for it.
I hope you get a more accurate reply, I never went to the extent of trying to re-wind one. I have heard of others building and having success by making "zapping device" using a couple of power transformers somehow hooked in series or something similar. The theory was that one could re-fuse the broken ends of the wire by introducing a high voltage just for an instant.