Explorer's Scope is a common Artifact — Equipment card from Commander Legends (CMR), collector number 461. Current market price: $0.29, TCGplayer market prices via Scryfall.
Whenever equipped creature attacks, look at the top card of your library. If it's a land card, you may put it onto the battlefield tapped. Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)