The Koffing (50 / 108) card can be found in the Evolutions set.
Recently sold 2 times and based on those sales is worth around £0.64.
Currently, there are 9 open listings for this card on ebay.
This card sells in the range of £0.42 to £0.86, making it very stable.
This Uncommon card was illustrated by Mitsuhiro Arita.