She had it on a ball chain around her neck, however occasionally she felt a tad self conscious about having a key hanging around her neck, visible enough for me to know that she held the key to her toy.
With my wife being a crafty person, I mentioned to her that she could create a charm to hang off my chastity cage, to remind me that my cock is actually her toy. However she took the idea and made it her own by creating the charm bracelet above to hang her key to her chastity cage.
I am wondering if she will end up making a charm to hang off her cage, I think the idea of being marked would be awesome, but then again, it would only be visible to her, plus anyone else she forces me to be naked around. We shall see if that ever happens.