The Steelix (35 / 147) card can be found in the Aquapolis set.
Recently sold 5 times and based on those sales is worth around £16.78.
Currently, there are 4 open listings for this card on ebay.
This card sells in the range of £10.29 to £23.27, making it quite stable.
This Rare card was illustrated by Hajime Kusajima.