Category:Stamps of Upper Silesia - Wikimedia Commons. The area of the then South-Prussian province Oberschlesien (French: Haute Silesie, English: Upper Silesia, Polish: Górny Sląsk, Czech: Horní Slezsko) was after the World War I according to the article 88 of the Treaty of Versailles (signed by Germany, 28 June 1919) occupated by Italian, French, and British military units under the ...