I've got a strong little magnet embedded in a dowel rod I keep on by brass prep table for just that. FWIW, I ran several through, loaded and shot 'em before I found out what was up. What finally tipped me was priming...pockets are tight on all S&B but on these, most are next to impossible to seat completely.
+1 on the tight pockets. I had a primer blow up on one when I was reloading, it was loud...
I would probably throw them out.