That' was the issue. After 1993 the WAM reverse was ONLY supposed to be used on proofs and the CAM reverse was only supposed to be used on business strikes. All of San Francisco's dies are made in Philadelphia and in 1998, 99, and 2000 at least one rev die hubbed for making proof coins (WAM rev) was accidently used to strike coins for circulation. In 1998 and 99 one business strike die (CAM rev) was accidentally sent to San Francisco, polished and used to strike proof coins. So the 1999 S with a WAM reverse is the normal reverse, the CAM reverse is the rare one. for 1999 business strikes the CAM reverse is normal and the WAM rev is the rare one.