The Dark Blastoise (20 / 82) card can be found in the Team Rocket 1St Edition set.
Recently sold 7 times and based on those sales is worth around £31.00.
Currently, there are 36 open listings for this card on ebay.
This card sells in the range of £16.13 to £45.87, making it quite volatile.
This Rare card was illustrated by Mitsuhiro Arita.