Cheat:

 In the game there's a dinosaur named Onno who plays a card game with
 you called TREBLE. You need to win two hands from her to get the
 necklace and the brass hinge you need to finish the game, but she's
 tough to beat when it comes to cards.

 Here's the cheat: Bet one of your possessions against one of Onno's.
 When the card game starts, press the back-apostrophe key [`] once.
 It won't make a noise or flash a graphic on the screen to tell you
 it's working, but Onno will get REALLY STUPID. You'll be able to win
 your trinkets from her with ease.