The Jolteon (6 / 100) card can be found in the Sandstorm set.
Recently sold 6 times and based on those sales is worth around £18.67.
Currently, there are 4 open listings for this card on ebay.
This card sells in the range of £10.43 to £26.91, making it quite stable.
This Rare Holo card was illustrated by Atsuko Nishida.