Cups of this type and period would originally have had liners made from silver sheet
Compare the similar cup dated 14th-15th century in the British Museum, illustrated by Garner, Chinese Lacquer, London, 1979, pl. 53 and another in the Museum of Far Eastern Antiquities dated 13th-14th century and noted as having a silver liner, illustrated by Jan Wirgin, 'Chinese Lacquer from Yuan, Ming and Ch'ing', Arts of Asia, November-December, 1981, p. 106