The picture you have is of an officer of The Royal Welch Fusileers, 23rd Regiment of Foot. They have the Prince of Wales crest and Regimental number engraved on their Gorget. Most regiment had some regimental device or the Royal Coat of Arms on their Gorget. G. Gedney Godwin and several other Sutlers sell them, only not regimentally marked. He is also improperly dressed as he has his sword belt over his epaulet. In full dress he would be wearing a Bearskin cap similar but slightly smaller than a Grenadier's.