srd.cards

Shield, +1, +2, or +3

Armor · Uncommon–Very Rare · SRD 5.2.1 p. 243

Armor (Shield), Uncommon (+1), Rare (+2), or Very Rare (+3)

While holding this Shield, you have a bonus to Armor Class determined by the Shield’s rarity, in addition to the Shield’s normal bonus to AC.