In THEORY
WAM cents could exist from 1994 to 1996 from Denver but none have been found. After 1996 I would say they would not be possible from Denver. Before 1997 Philadelphia provided Denver's dies and they could have sent a rev die from a proof hub. After 1996 Denver was making their own dies from Master hubs provided by Philadelphia. The only way they could have made a
WAM after 1996 would be if Philadelphia sent them the Proof master hub. And since there is only one master hub for each design I'm sure they would have noticed it missing. Besides if they did do it one year ALL of the Denver cents for that year would have been
WAM's. Someone would have noticed that by now.