Context. The porcelain is a large moon flat vase, from a private collection. The calligraphy is located inside a white rectangle, parallel to the mouth lip. The calligraphy is formed by 6 blue characters. I am sure that I correctly identified 5 of them. I am not sure of characters number 5 and 6, on the left side. I am not sure if due to the period of time they were made should they be read as they are 究旱徳宣明大, or in the modern way: 大明宣徳旱究. May be is a Ming Dynasty period vase. Please find attached some pictures and information.