Nystul's Magical Mask

source=Dragon Magazine #229

This spell has the opposite effect of Nystul's magical aura, covering up the aura of a magical item of up to five pounds of weight per level of the spellcaster. If an identify spell or other similar means is used to determine whether the item is magical, there is a 50% chance that the ruse is revealed. If not, all examinations of the item find it to be non-magical in nature. This spell does not work on extremely powerful magical items such as artifacts.

The components for this spell are a lump of coal and a drop of sour milk