Arcbound Prototype is a common Artifact Creature — Assembly-Worker card from Modern Horizons 2 (MH2), collector number 4. Current market price: $0.19 (foil $0.29), TCGplayer market prices via Scryfall.
Modular 2 (This creature enters with two +1/+1 counters on it. When it dies, you may put its +1/+1 counters on target artifact creature.)