According to L. Martin (p. 42 in J. Aruz, ed., Art of the First Cities, The Third Millennium B.C. from the Mediterranean to the Indus), "Among material from the end of the Uruk period and the following Early Dynastic period, stone vessels are, after cylinder seals, the most important sources of pictorial information...vessels of this type were frequently found in palaces or religious structures, which suggests that they had a special function in such settings." For a similar example see no. 12, op. cit.