It's smaller than a dime, it fits inside a living locket, or oragami owl necklace. I don't know which one you are familiar with, but if you search Listia for living lockets you'll be able to see the size of the charms that you put inside. I still have 1 locket I can list if you are interested.
I would like to see it, but I am looking for one I can put on a cord instead of a chain (any jewelry around my neck makes me break out) which reminds me...I really should list my chains now that I cant wear them anymore!