While the Biwat created a vast array of mask types, this particular example is part of an extremely limited corpus. Cf. one collected in 1928 by Merk-Ikier in the Museum für Völkerkunde, Berlin (inv. no. "VI 42361", Kelm 1966, vol. 3: ill. 209); a second previously in the collection of Marsha and John Friede and today in the National Gallery of Australia, Canberra (Sotheby's Paris, June 16, 2010, lot 8); a third in the Museum für Völkerkunde, Frankfurt (Stöhr 1972: no. 231); and a forth in the Museum Rietberg Zürich, Zurich (Bühler 1969: no. 23). According to Bühler (1969:86), this type of mask was displayed during initiation ceremonies together with the sacred flutes and the wusear ancestor figures. Like the ancestor figures, the masks were venerated as sacred objects possessing supernatural powers, and only initiates were allowed to see them (Mead 1984: 239).