Item levels

For the purposes of resolving magical battles the game assigns caster levels and spell levels to the effects created by magic items.

The caster level of an item determines the chances that its effects can be dispelled. The effects of wands, scrolls and potions count as caster level 10 spells for the purposes of dispelling them.

Some magical protections, like Globe of Invulnerability, protect only from magic of certain spell levels. When a mage protected by Globe of Invulnerability is attacked with a magical item, the outcome of the attack (whether the protection works or it doesn't) depens on the spell level of the item. In order to resolve this kind of battles, the game assigns spell levels to magical items. These are the spell levels of some items:
 * Wand of Cursing: 0
 * Wand of Wonder: 0 for haste, petrification, stoneskin, and strength; normal spell levels for Stinking Cloud, Lightning Bolt, Fireball, and Web
 * Wand of Missiles: 1
 * Wand of Sleep: 1
 * Wand of Fire: 2 (Agannazar's Scorcher) and 3 (Fireball)
 * Wand of Lightning: 3
 * Wand of Monster Summoning: 3, but it doesn't matter
 * Wand of Fear: 4
 * Wand of Paralyzation: 4
 * Wand of Polymorphing: 4 (I think this is only available with mods)
 * Wand of the Heavens: 5
 * Wand of Frost: 5
 * Wand of Cloudkill: 5
 * Wand of Spell Striking: 5 (Breach) and 6 (Pierce Magic)
 * Rod of Reversal: 7
 * Oil of Fiery Burning: 0
 * Potions of Explosions: 0
 * Necklace of Missiles: 9