Continuity mistake: As Jack presents Joan with the necklace when they are seated at dinner during the festival scene, the one he is holding in his hand is a beaded necklace, to attract more light for the further camera shot, only when the close up of the table occurs it is a completely different necklace. (01:06:55)
Suggested correction: Jack actually hands her a lot of necklaces not just one, Joan picks out only the one with the heart and puts it on. Of course we know why she chooses that one, but if you look when they get up to dance you can see the other necklaces in a pile on the table, pearls included with the other gold necklaces. I always wondered why he just didn't buy her the one, why did he buy her the bunch then just leave them on the table? (Yes I'm sure they got them when they were done dancing).