There are some inconsistencies with the skill rings we currently have.
The following progressions apply to Alexandrite, Sapphire and Topaz jewelry.
Skill rings: Bronze +2, Silver +4, Mithril +6
Exceptional Skill Rings: Bronze +2, Silver +4, Mithril +6
Skill amulets: Bronze +1, Silver +2, Mithril +3
Exceptional Skill Amulets: Bronze +2, Silver +4, Mithril +6
So the amulets still use the old progression and the Exceptionals for both rings and amulets follow the new progression for normal skill jewelry.