What goes in the skull?

Hello all :smiley:, I have this thing lol which I believe is a waistcoat fob kind of thing. but I do not know what the silver mark means. Also the skull fastens with a pin as shown in the first photo (the small pin on the left slots through two loops to close the skull. but does anyone have an idea what would have been kept in the skull part? And if anyone could tell me what the silver mark is I would be very grateful. Just added another photo, doh am I due for an eye test or what. In the bottom jaw of the skull, there is a picture carved out looks like a swan or a snake and a sun. does this help anymore to identify it? My eyesight is not very good.

Thanks
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I’m not an expert, so don’t take this to heart. Maybe it was used for tobacco? It is kind of creepy, do you know where exactly it comes from? More information might help determine more about it.