Both coils are copper.. Went to a new scrap yard today to sell a load of steel and weighed the two coils. 7 lbs out of a 20 lb transformer. They offered me $2.35 lb for every coil. That's with them having tape and glue residue. Think I'm just gonna tear them all down over winter and cash in when copper rises again. Needless to say, it was a good day considering these transformers are worth $16.45 a peice instead of the .35 lb I was going to sell them for.