Update on provenance:

The work appears to be a copy of Wilhelm Dittmer's (1866 - 1909) 'The Keeper of Mere Pahikaure, Te Rerehau Kahotea'.

That work is illustrated p. 225, Colonial Constructs - European Images of Maori, 1818-1914, Leonard Bell.

The Mere Pahikaure is the most treasured trophy of the famous Ngatitiwharetoa tribe and the stories of its capture and recapture are long and sanguinary. The mere is of greenstone, about 18 inches long and beautifully made. Greyish veins run through the greenstone and the tribe believes that the approaching death of its chief is signalled by the darkening of its veins. Te Rerehau Kahotea, The Keeper, a rangatira of long descent is the wife of the distinguished chief Te Heuheu Tukino'. By courtesy of the Christchurch Press. Biographical note: Wilhelm Dittmer was born in Hamburg in 1866. He studied art in Munich and Paris and in 1898 he came to New Zealand where he remained for seven years during which time he lived amongst the Maoris. He wrote and illustrated Te Tohunga -The Ancient Legends and Traditions of the Maoris, published by George Routledge & Sons, London, 1907. Dittmer painted fourteen Maori portraits of which the portrait here was reproduced as a colonial lithograph and as a postcard by Whitcoulls. Dittmer returned to Hamburg where he died in 1919.