This object is an antique aqua glass bottle stopper.  These stoppers were used for various types of bottles, including decanters, perfume bottles, and food containers like those for sauces. It features a rounded, flat-topped "head" and a tapered stem designed to fit into a bottle neck.  These were commonly used for brands like Lea & Perrins or Holbrook & Co. for sauce bottles. 

Please review condition details and pictures prior to purchase.

I am always happy to consider any reasonable offer and will combine shipping.