User blog comment:Broman178/Merlin's ability to sense magical objects./@comment-5350801-20120810200712

Don't forget that in Beauty and the Beast Uther had that enchanted pendant from the troll and Merlin did not sense that either.

I wonder if it's more that he can sense powerful magical objects. Every time he was able to sense magic, the Mage Stone, Rowan Staff, Phoenix Eye, The Cup of Life, the magic was VERY powerful. I would think an enchanted pendant or bracelet would be so low level it wouldn't even register.