I want to sell my ex boyfriends coin and stamp collection and I want to make sure he can not trace the sale.?

He gave me collection (which is fairly valuable, during our better days. We broke up after he cheated with another woman. He is a charmer and I am afraid I might fall for his charm again and give them back. I want to punish him, buy selling the collections to a buyer that he would never be able to contact and try to buy his precious coins and stamps back. Just for info, I am 25 years old and never been married. I could use the money and selling them would help my financial situation and hurt him in a special way that he could not recover, since his cheating hurt me.