The Saint Christopher medallion is different from the one that Merrin found at the dig in Innevi, Iraq. The medallion is seen in three specific spots in the film: Northern Iraq, Karras’ dream sequence, and the final exorcism scene when Regan pulls it from Karras’ neck. I may have missed one or confused the medallion (yet I think they are all the same being that of Saint Christopher). I think it’s a wonderful way that Blatty and Friedkin reached out to us in a religious metaphoric-type way throughout the movie … plus it was another eerie thing to add to the pulse of the movie. I always think of the medallion as having a writer’s true beginning (discovery in Iraq), middle (forthcoming of evil in Karras’ dream sequence), and ending (the demon needing to rid Karras of anything holy before entering his body).
Just thoughts … anybody else?