Just found this on the internet. Though it may be too stupid for me to ask, is the top polished? or is this really a specie of cypraea. Looks like a polished caputserpentis.

http://www.badongo.com/pic/683460

Yes this is Cypraea caputserpentis.  They are sold in this condition in the shellcraft trade, as "purpletop cowries".

For example:  

http://www.shelloutlet.com/cowrieseashells.html

Thank you Paul. I thought so. I was just confused because I sent a message to the seller but he insisted it is all natural. 100% natural.