The Mewtwo (12 / 113) card can be found in the Delta Species set.
Recently sold 2 times and based on those sales is worth around £33.88.
Currently, there are 11 open listings for this card on ebay.
This card sells in the range of £32.77 to £34.99, making it very stable.
This Rare Holo card was illustrated by Ryo Ueda.