Ok, that was going to be my guess. I think that's cool, looks like CC included it as a gift to show off a prototype or whatever.
Yeah. I'm glad they complement each other. And at the end of the day, it has a stamp and the dots
So is it part of the mold?
I don't think so. It feels like it has been added on the top. I can't really take a picture of it as I only have a phone, but if you zoom right in on the picture of the two facing the camera (full size here -
http://i.imgur.com/VzNaFqN.jpg) you can juuuust see on the very top of the grey one that the skull goes slightly over the rim of the cap itself. This is more prominent at the bottom, as it looks like it's been applied like 1mm too far down.
I have tried peeling it off, but it feels like it's stuck on there real good. Not sure how as there really isn't much room to get a fingernail under there, but it's definitely not part of the cap itself, as that is textured and the skull is smooth.