A fun fact about magic items that cast spells is that in every case I've seen they are listed as one rarity higher than a spell scroll for that spell. Enspelled Armor/Weapon/Staff starts as an Uncommon for Cantrips and First Level. The Hat of Disguise (level 1 spell) is Uncommon, +1 rarity compared to the scroll. Boots of Levitation (level 2 spell) is Rare +1 rarity. Necklace of fireball (level 3 spell) is Rare. Wand of polymorph (level 4 spell) is Very Rare. It's always +1 rarity from spell scroll. Judging it based on every other item that the ability is "cast X spell" this helmet should be Legendary, because that's +1 rarity when compared to the same spell on a scroll.

Just got shown this. I don't comment often but I just....A scroll of teleport, a single use item, is very rare. This helm, which gives up to 3 uses a day, is rare. What? I'd easily call this legendary honestly. 

I just realized the most overpowered mechanic involved with this item if it is crafted as an Infusion for an Artificer at level 14 using the new rules. 

This is the ability that was posted: Charge Magic Item: As a Bonus Action, you can touch a magic item within 5 feet of yourself that you created with Replicate Magic Item and uses charges. You recharge the item and expend a level 1+ spell slot. The number of charges an item regains is equal to the level of spell slot expended.