From High Roller Guides

Double Wammy is a classic 3 reel, 3 coin 1 payline slot by Microgaming. The max bet only wins you a little extra if you hit the jackpot, which pays out 2500 if you get the winning combination of the double wammy symbol which is of 2 diamonds nesting on the "DOUBLE Wammy" logo. Other symbols are the classic BAR, cherry and 7s.

Wild Symbol: The Double Wammy is a wild symbol.

Multiplier Symbol: The Double Wammy is also the multiplier symbol, a single "Double Wammy" symbol doubles the payout whilst two Double Wammy symbols quadruple the payout of any combination they complete.