Brass Knuckles is a uncommon Artifact — Equipment card from Fallout (PIP), collector number 227. Current market price: $0.30 (foil $0.53), TCGplayer market prices via Scryfall.
When you cast this spell, copy it. (The copy becomes a token.) Equipped creature has double strike as long as two or more Equipment are attached to it. Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)