The Gyarados ex (109 / 112) card can be found in the Firered and Leafgreen set.
Recently sold 3 times and based on those sales is worth around £39.44.
Currently, there are 7 open listings for this card on ebay.
This card sells in the range of £0.01 to £83.57, making it highly volatile.
This Rare Holo Ex card was illustrated by Hikaru Koike.
The fact that it is a EX card makes it one of the more valuable cards.