I was recently going through my accumulation of UK 2-pence coins and sorting then by their composition-- 97% copper for coins minted up through 1991, and copper-clad steel for coins minted 1992 and later. The easiest way to separate them with these compositions is with a magnet. The steel coins stick to the magnet, while the copper coins do not stick. After a while, I came upon a 1998 2-pence coin that would not stick to the magnet, or any other magnet that I tried. After much searching, I found another 1998 and sure enough, it stuck to the magnet with no problem. On the non-magnetic 2-pence, there is no obvious sign of tampering. What could explain the non-magnetic character of this 1998 2-pence coin?