A: You asked about quality, value and authenticity. The quality, (if that means appearance), is very good in my personal opinion. The value would depend on whether it was carved with natural tools or steel tools. It is very difficult for me to answer this when I can only look at 72dpi scans.
Notice that the rear of this very traditional Sepik River area mask is flat. That is because many of the various ethnic groups also use masks to hang on their huts or men’s meeting houses.
Also of interest is that most of these people never were disturbed by white people until the middle of the 20th century. So a pre-discovery mask carved with a sharp stone or shark’s tooth might only be 50 years old. On the other hand, the indigenous people quickly learned how to make old-looking items that the new visitors were willing to trade for wonderful stuff like pots and pans, knives and chisels, and MONEY.