Thanks for your responses everybody! It just seems weird to me. I called customer service and they were nice but not exactly reassuring. She told me that sometimes they change the designs from year to year and that she was fairly sure that it was authentic but she wasn't able to pull up a picture of it that didn't have a hallmark even though they usually are marked. One way or another I took it back to a Tiffany store and they are going to send me a brand new one because the clasp was broken either way and I shouldn't have to wait for a repair on something that was supposed to look brand new. It was a good thing the SA knew me because she definately gave the necklace I brought in a good long look until I told her what customer service told me. I can imagine that it all looked very suspicious to them but no one indicated that they thought so. I hope either way that the one hey sende is marked but if it isn't at least I'll know it wasn't a fluke.