See you write when Morrison lost to Mercer in '91 that Mercer relinquished his title shortly after...
As I remember, he was still WBO champion when he fought Larry Holmes, but the WBO wouldn't sanction the fight. (the reason why it was a 12 rounder, if no title was considered it would have been a 10 rounder)
Think the WBO stripped Mercer just before he entered the ring...
Moorer was the no 1 contender, but if my memory serve me correctly, it was supposed to be a WBO title fight, but the WBO didn't sanction the fight. And stripped Mercer in the last minute.