1918 Overprints on non-issued Warsaw city postage stamps from 1916 (1):

 

1919 North Poland issues (2):

 

1919 South Poland issues (3):

 

1919 issue for Western Galicia:

 

 

1: 1920 Definitives: Eagle on a baroque shield
2: 3 Mk overprint (1921)
3: 1921 Sowing man (large format)
4: 1921 Sowing man (small format)
5,6: 1921/23 Eagle on a large baroque shield
7-9: Inflation overprints (1923)
10: 1924 Eagle on a large baroque shield (4)
11: Eagle in laurel wreath (1924) (5)
12: President S. Wojciechowski (1924) (6)

 

1921 Aero-Targ Air Post Stamps (7):

 

 

1: 1925 Airmail: Airplane over Warsaw
2-7: Buildings & Monuments (1925)
8: Marshal J. Pilsudski (1928)
9,10: J. Pilsudski and I. Moscicki (1928)
11: 1929 Eagle (solid background)
12: 1932 Eagle (striped background)
13-15: Overprints due to redefined postal rates (1934)
16-25: Sights and I. Moscicki (1935)

 

1-4: Views and buildings (1937)
5: 1939 Definitive stamp (8)

 

 

 

(1) The text "Poczta Miejska" (city postage) is overprinted with "Poczta Polska" (Polish postage). Polish Fenigow denominations are used (100 Fenigow = 1 Marka), derived from the German Pfennig and Mark.

(2) On former German occupied territory, the northern part of Poland, stamps were issued in Fenigow/Marek currency.

(3) On former Austrian occupied territory, the southern part of Poland, stamps were issued in Halerzy/Korony currency.

(4) Poland was caught in the hyperinflation of the early 1920s and was forced to print stamps in ever-increasing denominations, topping out at a 2,000,000 Marek value in 1924.

(5) The hyperinflation of after war years was overcome with introduction of a new currency. The old Fenigow and Marek are now replaced by Groszy and Zloty.

(6) Stanislaw Wojciechowski (1869-1953) was a Polish politician, president of the Republic of Poland (1922-1926). Initially one of the founders of the Polish Socialist Party, he later left the party and was involved in growing cooperatives movement. After he was ousted by Pilsudski's coup d'etat in 1926 he retired from public life and returned to his university post at the Warsaw Agricultural University.

(7) The Aerotarg company, following an agreement with the Polish Ministry of Post & Telegraph, issued these stamps. It was agreed that in addition to the normal express postage rate, payable by the use of normal Polish stamps, there would be an additional payment for airmail, payable by the use of the Aerotarg stamps. The agreement was for the period of the Poznan Trade Fair in 1921 on three routes. The first flights started on 29 May 1921. Then there were daily return flights till 16 June 1921 inclusive. Plans to continue these flights were not realized.
The stamps were designed by Wilhelm Rudy (hence the initials W.R. on the stamps). The 25mk value shows Icarus against a silhouette of Poznan and the 100mk shows a Junker F3 dropping mail over Poznan. The stamps were roughly lithographed and many small defects in printing may be found. The total printing was 50,000 of each value but very few of these were used genuinely.
The stamps were sold in post offices Warsaw 1, Poznan 1, 3 and 9. In accordance with the agreement the normal postage stamps were postmarked with the post office postmark. The Aerotarg stamps were obliterated with a special postmark produced by Aerotarg.

(8) This stamp is similar to the 15gr stamp from 20th Anniversary of Independence set. Nazi Germany forced Poland to remove the swords and helmet at the feet of the king Wladyslaw II Jagiello and queen Jadwiga from commemorative stamp because they claimed the design to the Universal Postal Union.