Based on accompanying field notes and a handwritten label, this particular head is believed to be a “kovakieto” associated with crop fertility rituals.Based on accompanying field notes and a handwritten label, this particular head is believed to be a “kovakieto” associated with crop fertility rituals.

Artvisory's James Parkinson with one of five rare Tabar Island "heads" that will be auctioned next month in Auckland. Photo / Corey FlemingArtvisory’s James Parkinson with one of five rare Tabar Island “heads” that will be auctioned next month in Auckland. Photo / Corey Fleming

A young Dr Augustin Schiessel and one of field journals he kept during his time as a medical officer in New Ireland, Papua New Guinea. Photo / Corey FlemingA young Dr Augustin Schiessel and one of field journals he kept during his time as a medical officer in New Ireland, Papua New Guinea. Photo / Corey Fleming

William "Bill" Schiessel is selling the tribal art collection his father Augustin amassed in 1949-50 as a medical officer in New Ireland, Papua New Guinea. Photo / Corey FlemingWilliam “Bill” Schiessel is selling the tribal art collection his father Augustin amassed in 1949-50 as a medical officer in New Ireland, Papua New Guinea. Photo / Corey Fleming

 Dr Augustin Schiessel and Elizabeth Aitken MacCormick lived in New Ireland in 1949-1950, with their three children (from left) Richard, William and Donald. The family dog Lumpi often accompanied the doctor on his patrols. Dr Augustin Schiessel and Elizabeth Aitken MacCormick lived in New Ireland in 1949-1950, with their three children (from left) Richard, William and Donald. The family dog Lumpi often accompanied the doctor on his patrols.

One of two kovabat or "rain heads" believed to have been specifically described by Dr Augustin Schiessel in a letter he sent to Auckland in September 1950. One of two kovabat or “rain heads” believed to have been specifically described by Dr Augustin Schiessel in a letter he sent to Auckland in September 1950.

 After his return from New Ireland, Dr Augustin Schiessel (far left) practised medicine in Kaikohe. Middle son Bill stands to the left of the day's catch. After his return from New Ireland, Dr Augustin Schiessel (far left) practised medicine in Kaikohe. Middle son Bill stands to the left of the day’s catch.

 William Schiessel remembers this carved wooden frieze (which has a pre-auction estimate of $10,000-$30,000) being displayed in his parents' homes. William Schiessel remembers this carved wooden frieze (which has a pre-auction estimate of $10,000-$30,000) being displayed in his parents’ homes.

Some of the treasures unearthed in preparation for the sale of The Dr AA Schiessel of New Ireland and Oceanic Art in Auckland on July 27. Photo / Corey FlemingSome of the treasures unearthed in preparation for the sale of The Dr AA Schiessel of New Ireland and Oceanic Art in Auckland on July 27. Photo / Corey Fleming