Ancient Gear Tank is a Equip Spell Card.
Spell Cards are usually activated from the hand on your turn unless their type gives another timing window.
On the current TCG and OCG Forbidden & Limited lists tracked here, Ancient Gear Tank is Unlimited.
YGOPRODeck lists Ancient Gear Tank for these formats: Duel Links, Common Charity, Edison, TCG, OCG, Master Duel.
Ancient Gear Tank belongs to the Ancient Gear archetype—use that tag when searching for engine pieces and tech options.
A listed print of Ancient Gear Tank appears in Structure Deck: Machine Re-Volt (SD10-EN018) at Common rarity.
Among markets shown on this page, the lowest listed snapshot for Ancient Gear Tank is about $0.54 on Cardmarket (prices change frequently).
