Knowledge of the development of this separate African culture is far from complete but some of the earliest objects excavated so far date from the 12th and 13th Centuries, while others, notably those attributed to the Benin Kingdom, appear to have been cast between the 15th and 17th Centuries. A tomb recently excavated at Igbo in Eastern Nigeria contained a hoard of bronze objects including a number of highly decorated bowls and vases, pendants, amulets and ornaments which had been buried with the priest-king as part of his ritual regalia. Also recovered at the same site were examples of pottery, specimens of textiles and pieces of calabash. In this respect it is worth noting that the preservation of these organic materials is almost certainly due to the presence of copper in the bronzes which inhibited the action of white ants and bacteria. The most highly valued examples of West African bronze work are undoubtedly the cast heads, one of which is shown in Fig. 13. These have an almost classical style and show a mastery of technique which has rarely been surpassed.