The Rocket's Entei ex (97 / 109) card can be found in the Team Rocket Returns set.
Recently sold 2 times and based on those sales is worth around £27.39.
Currently, there are 2 open listings for this card on ebay.
This card sells in the range of £15.00 to £39.78, making it quite volatile.
This Rare Holo Ex card was illustrated by Ryo Ueda.
The fact that it is a EX card makes it one of the more valuable cards.