Doesn't the "C" on a vintage Jensen C15N Speaker frame indicate that it's a ceramic magnet and not an alnico magnet? If you look at the picture, the label says it's an alnico magnet, but stamped on the frame is C15N which indicates it's ceramic. Is the frame stamp correct or is the label transplanted from another speaker? I'm not expert enough to determine which kind of magnet it is by appearance, although I know alnico magnets that are used on speakers are smaller in diameter than a ceramic magnet. The date code suggests it's was made in the 14 week of 1962. The seller said it was pulled form a B-15N.