The Gyarados (6 / 16) card can be found in the Pokémon Rumble set.
Recently sold 1 times and based on those sales is worth around £43.43.
Currently, there are 2 open listings for this card on ebay.
This card sells in the range of £43.43 to £43.43, making it very stable.
This card was illustrated by Pokemon Rumble.