who designed it?
John, Duke of Berry
Royal Gold Cup
 The said hanap and cover were given to the king by monseigneur the duc de Berry on his journey into Touraine in the year 91.
John, Duke of Berry (1340–1416) was Charles VI's uncle and a powerful figure in the kingdom, as well as the most famous and extravagant collector and commissioner of art of his day.
what is royal gold cup? It is a solid gold covered cup lavishly decorated with enamel and pearls. is it kept in a museum? Yes, in the British Museum
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Royal Gold Cup [SEP] Provenance
How he acquired the cup is not known, but he would have received many gifts from Charles VI, and had both lent the king money and bought from him things such as the library of the Palais du Louvre, in the uneasy period when Charles had made peace with the English and made Henry V his heir. After the death of his brother Henry V, Bedford struggled to stem the resurgent French resistance, which was energised by Joan of Arc. He died in Normandy in 1435, leaving Henry VI as his heir. The cup is more briefly described as the first item in a list of valuables received from Bedford's estate prepared for Henry VI's minister Cardinal Henry Beaufort, but the tripod is not mentioned, some of the jewels are missing, and the subject is misidentified as the life of Saint Suzanna not Saint Agnes.