Coat of Arms is a rare Artifact card from Secret Lair Drop (SLD), collector number 1712. Current market price: $20.66, TCGplayer market prices via Scryfall.
Each creature gets +1/+1 for each other creature on the battlefield that shares at least one creature type with it. (For example, if two Goblin Warriors and a Goblin Shaman are on the battlefield, each gets +2/+2.)