Bone Saw is a uncommon Artifact — Equipment card from The Brothers' War Retro Artifacts (BRR), collector number 7. Current market price: $0.14 (foil $0.61), TCGplayer market prices via Scryfall.
Equipped creature gets +1/+0. Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)