What is the golden apple?

In professor layton and the curious village, the professor and his apprentice Luke are in search for the Golden Apple. In the end, The golden Apple is revealed to be the late Baron's only daughter, Flora. The Baron was clever and made it a mystery as to where or how to obtain the fortune exactly. The person who found his daughter wasn't the only qualification. If you make Flora (or as the Baron calls her, "his Flower") smile or laugh, a golden Apple appears on her neck. The painting of her in Reinhold manor is the key to the fortune.