Yes, it is Greenland, The post delivery from or to the Thule region was handled by the Cape york office in Copenhagen where the post could be handed in or collected. Then it could be forwarded from the office by post if the letters were also franked with Danish stamps. In August 1937 the Greenland admin. took over the Thule region and the stamps were invalid.
The set with 5 (10,15,25,20,40 ore) stamps is listed in Michel and other European catalouges. The value for a MNH and a used set is the same (40 Euros).
"The Thule stamps were issued in 1935 at the Thule community at the extreme north western part of Greenland. This society, consisting of only 400 souls, was studied very carefully by the arctic explorer Mr Knud Rasmussen, who in 1910 had established a small trading post in Thule. To support this small society, a Thule Committee was founded in Denmark. In 1935 it issued a set of four stamps which were to be used on mail carried to and from Thule on the small ship "SØKONGEN" which was owned by the committee.
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In 1936 a supplementary value was issued.
The stamp ceased to be valid at the end of July 1937 (a few covers from early August are known). Parcel post stamps were used for a few years until postage stamps were introduced.
Of course this issue has been sold mainly to collectors - either unused or cancelled to order - but it has also served a legitimate postal need. Postally serviced covers with both Danish and Thule franking are quite rare."
THe original set consists of the three stamps in the scan plus a vertical 15øre red stamp showing the Danish flag with a sailing ship in the background.
The 1936 value is a horizontal 25øre lilac stamp, showing people going to church, in the same format as the 45øre stamp but with the heading "1936 - THULE - 1936".
I understand that these were for a valid postal use and that Scott does not list them. There are 4 values inthe set and the 15 ore red is what I am missing. The eBay linked stamp is no longer listed. The listing closed last in February.
It looks like I will have to prepare a page for these and continue to hunt for the 15 ore and the subsequent set!
My understanding is that the sale of these stamps was to help pay for mail transport in both direction from the THULE station and the main office in Copenhagen. Thule was a trading station set up in 1916 to trade for furs with the Eskimos. Today I believe that Thule is a US air base. The inhabitants were relocated farther north in Qaanaaq