The Mystery Plate (134 / 144) card can be found in the Skyridge set.
Recently sold 2 times and based on those sales is worth around £2.10.
Currently, there are 4 open listings for this card on ebay.
This card sells in the range of £2.00 to £2.20, making it very stable.
This Uncommon card was illustrated by Hiromichi Sugiyama.