LionHeart: Legacy Of The Crusader Change treasure
Press [F9] to quick save the game when you find a chest. Lock pick or open the chest. Reload the game if you do not get a desired item. Open the chest again and the item will be something else. Repeat this until you find the desired item.
The image featured at the top of this post is ©The Legend of Heroes: Trails of Cold Steel III key art / Original