On January 5, 1930, the PORT GDANSK overprint was applied to the 1928 Henryk Sienkiewicz issue of Poland, as shown above, at the left (Mi. #24, Sc. #1K23).
Henryk Adam Aleksander Pius Sienkiewicz (1846-1916) was a Polish journalist, Nobel Prize winning novelist, and a philanthropist. He is best known for his historical novels, the best known of which is his monumental work called Quo Vadis.
The 1 Zl. Mościcki stamp was again overprinted on July 1, 1933. On this issue though, the two lined overprint is applied in dark blue to each side of the stamp, as shown above, at the right (Mi. #25, Sc. #1K24). This particular version is much better, as it leaves a clear view of the subject which had been obscured by the former horizontal format overprint used in 1929.
Between October 1934 and October 1935, the three Poland Arms definitive stamp issues of 1932-1933, shown above (Mi. #26-28, Sc. #1K25-27), were overprinted for Danzig.
Between August 1936 and October 1937, the 5 Gr., 15 Gr., and 25 Gr. denominations of the 1935 Poland Scenic definitive series were overprinted for use in Port Gdansk (Mi. #29-31, Sc. #1K28-30).
The 25 Gr. denomination was printed from two plates. The designs of the stamps from Plate I, issued in 1936, were 28.3 x 21.3 mm. The designs of the stamps from Plate II, issued in 1937, were 28.5 mm x 22 mm. Both of them are shown above (Mi. #31I-31II).
On June 5, 1937, the 5 Gr. and 15 Gr. denominations of the Poland 1937 scenic definitive set were overprinted for use in Danzig. They are both shown above (Mi. #32-33, Sc. #1K31-32).
On November 11, 1938, the first set of postage stamps actually printed for the Polish Post Office in Danzig were issued. The four stamps, shown above (Mi. #34-37, Sc. #1K33-36), were issued to commemorate 20th Anniversary of the Founding of the Republic of Poland. They all have the same design, with that being a painting of Polish Merchants Selling Wheat in Danzig in the 16th Century.
The Polish post offices in Danzig were closed on September 1, 1939, following the annexation of Danzig by the Third Reich.