This medallion is an exact copy of that from the new game The Witcher 3: Wild Hunt
bigger wall plaque accessible here
The Witchers' Medallion is a silver symbol of the witchers field. It's senstitive to magic, pulling and vibrating on its chain when spells are being cast or charming beings, like genies, are present. This magic medallion formed like a wolfs head is granted to every youthful witcher nominee who has passed The Trial of the Grasses. The source of the first medallions is not known, though it's supposed they were made in the magic forge at Kaer Morhen. The medallions vibrate in response to magic in all its forms, including charms, curses and enchantments. Additionally they warn of lurking creatures born of experiment or magic.