Well looking in the shell of this supraphonic you see this:
[IMG]http://i214.photobucket.com/albums/cc232/tradjazzS/100_0195.jpg[/IMG]
It is consistent in all 360 degrees of the drum in just that bottom part. Is that some kind of oxidation that occurs, it doesn't look like rust. And it can't be brass because I am sure that the shell is not COB, since the pitting it has, although lately I have been debating about if the hoops were.