Commander's Plate is a mythic Artifact — Equipment card from Commander Legends Promos (PCMR), collector number 305p. Current market price: $48.75 (foil $58.45), TCGplayer market prices via Scryfall.
Equipped creature gets +3/+3 and has protection from each color that's not in your commander's color identity. Equip commander {3} Equip {5}