Revealing mistake: The clasp closure on the medallion's chain is NOT the sort that just comes apart when yanked on, evident in the many close-ups of the clasp throughout the film. Yet there are a number of scenes in which the chain is just pulled and it comes off easily: Elizabeth pulls it off aboard the Pearl, to barter with; Barbossa pulls it off, during her blood ritual; Elizabeth pulls it off to give to Will, aboard the Interceptor... The chain was secured to her neck with sellotape, in order for it to come off quickly for the shots. (01:12:15 - 01:19:28)