Fools' Copper

source=Dragon Magazine #229

This spell is the reverse of fools' gold, making items appear less valuable to creatures viewing them. The disguise does not alter the nature of the item (gold is still gold, diamonds are still diamonds), but it lowers the perception of an item's quality. A jewel-encrusted golden ring could be made to look like a plain iron band with this spell, and a rune-carved paladin's long sword could appear as a rusty peasant's blade. The saving throw and other elements of the spell are the same as fools' gold, including the use of powdered gemstones to make the spell harder to detect.