This unusual button yo-yo was originally sold at the Charmore Hotels, in New York and Paris, very elite hotels. At a time when yo-yos were the fashionable thing to have. It has an interesting clip on string end, to be attached to the yo-yo for storage, and used to make the string loop when playing. The body is Gold Plated.
I've heard various stories about these, regarding age and quantity. One story tells of a party at the hotel Charmore in New York in the mid 30's, when Don Duncan Sr. gave these to all the guests. But they were also sold at the hotel gift shop. So it is uncertain if these were made by Duncan.
Several people have mentioned winning these from Don Duncan Jr. in the 1950's in Duncan Contests. So apparently Don had a good supply of them at Duncan. But were they made by Duncan, or did he acquire some inventory from Charmore, or from his father? More questions than answers on this unique piece.