Hubley Antique Duck Childs Door Stop/ Nut Cracker/Toy. Antique Hubley childs cast iron duck doorstop has many uses. Originally the cast iron duck was advertised childs door stop. It was also used as a nut cracker and toy. The duck stands 5 inches. This duck has been loved so please look at the pictures as to. This duck has been in my collection for 30 years. It is time for my collecttions to be passed on to you.