At the end when they show the flashback of when Tristan and Isolde are in Ireland and Isolde is reading her poem, Tristan kisses her and she holds up her hands and she is not wearing her shell bracelet. But earlier in the movie during the same scene she is wearing it. See more
Britain. The Dark Ages. / The Roman Empire has fallen / The land lies in ruins, divided among feuding tribes. / To the west, Ireland has flourished - untouched by the Romans, protected by the sea. / Led by their powerful and righteous king, the Irish have subdued the Britons... / Knowing that if Ireland is to prosper, the tribes must never be allowed to unite.