ORIGINAL: John Palica
If they attract to a magnet they are steel and will likely corrode. If they don't get attracted by a magnet then they are likely stainless or brass. However some low grade stainless will still be lightly attracted by a magnet.
300 series stainless steel is not magnetic. 400 series is. It has to do with the content of nickle in the stainless. I simply dropped it in a glass of water overnight to test. It rusted. To bad because it looked really good turned. Good size to. I used my handy dremel combo sanding station to turn it (I don't think they sell them anymore - its been a real handy tool.)/.