The Magic Hoard - Ring of Grand Wizardy

Ring of Grand Wizardry: This ring allows a Magic User to memorize spells of a higher level than normal. For example, a 3rd-level Magic User (2-1st / 1- 2nd ) with a +2 Ring of Grand Wizardry could memorize (0-1st /1-2nd /2-3rd) or (2-1st /0-2nd /0-3rd /1-4th) as the ring increases one spell level of his casting ability by 2 levels, thusly turning 1st level spell slots into 3rd level spell slots or 2nd level spell slots into 4th level spell slots. Only one level of spells can be increased with a Ring of Grand Wizardry, except in the case of the +1/+2 Ring.

Power                X.P Value        G.P. Value
+1 Level             4,200                52,000
+2 Levels            4,800                58,000
+3 Levels            5,000                60,000
+4 Levels            5,400                64,000
+1 Level             4,800                58,000
and +2 Levels