The Vaporeon (19 / 115) card can be found in the Unseen Forces set.
Recently sold 5 times and based on those sales is worth around £10.50.
Currently, there are 10 open listings for this card on ebay.
This card sells in the range of £3.91 to £17.09, making it quite stable.
This Rare Holo card was illustrated by Atsuko Nishida.