From 1915 through '23, Australia issued 49 stamps for a group of islands in the Pacific called the North West Pacific Islands by overprinting Australian stamps.
These range in value from inexpensive (under $10) to $ for the key stamp, the 1916 2 1/2p Dark Blue with wide crown and narrow "A" watermark (Scott #14).
While quantities issued information is unavailable for most N.W.P.I. stamps, I estimate that those which catalog over $100 had printings in the low thousands or fewer. Since these are all overprints, I advise purchasing them conditional on obtaining expertization if there's any question as to whether the stamps under consideration are authentic. I recommend purchase of the better N.W.P.I. stamps (those which catalog $200 or more).
While the stamps appeal to British Commonwealth collectors generally, the main catalyst for their growth will come from the Australian market. In Australia, the Pacific island nations or territories which the Australians administered or for which they issued stamps are viewed, from a philatelic perspective, in the same way that European collectors view their former colonies.
Australia is a prosperous nation of 22 million people and a diverse economy, with thriving service, agricultural, and mining sectors. Annual GDP growth has average 3.6% over the past 15 years. Recently, there has been considerable growth in mining and petroleum extraction, in part due to increased exports to the resource-hungry Chinese market. It is likely that Australia's stamp collecting population will grow significantly as the nation ages. The percentage of Australians over 60 is projected to rise from 16% in 2000 to 24.8% in 2025, and 28.2% in 2050.