I just checked the one in the Kit that I Posted earlier. It is not attracted to a magnet, and if I were to guess without a lab test, I would say it is mainly, if not completely, Copper. No apparent coatings. Even in a Zip-lok for several years since that picture was taken, it has tarnished just as Copper does.
Interesting, since the ones on my 57's and 59's are solid, "springy" Brass. Makes me wonder when Ford made the change.
Bob