A porcelain cup is an item in Evony TKR (The King's Return).
Porcelain Cup is one of the collection items in the exhibition for the Art Hall. It is one of four parts in the Cup Hall. After the set is completed at three stars, you can trade additional Porcelain Cup fragments for gold.
The description of Porcelain Cup in Evony TKR says:
Cups made from different textures. The important exhibits in Cup Hall.
Porcelain Cup is known to potentially be obtainable from opening Artwork Fragment Chest IV, Artwork Fragment Chest V and Artwork Fragment Chest VI. The links for each item are below:
Note: This list may be incomplete.