Postage stamps

After 1918 both Czechoslovakia and Poland claimed the Těšín region. For the planned plebiscite both countries overprinted their stamps S.O. 1920 – Silésie Orientale, Eastern Silesia – and they were in use from February to September 1920. The vote never took place: the border was settled by the powers on 28 July 1920.

Sources: Wikipedia: Eastern Silesia, znamky.cz: SO 1920

Two imperforate express stamps by Alfons Mucha, the 2 and 5 h on pale yellow paper, also received the SO 1920 overprint, in blue or black – specialists distinguish several shades of the blue. 380,000 of the 2 h and 300,600 of the 5 h were overprinted. The issue dates are unknown, and so few genuinely carried covers exist that the period of use is hard to establish; the earliest known date, 13 March 1920, comes from a philatelic cover.

Sources: Burda Auction: SO 1920

Mucha's flying-falcon newspaper stamps were overprinted SO 1920 as well. The Czechoslovak overprints were issued from 13 February 1920 and were valid only at Czechoslovak post offices in the plebiscite area, until 10 August 1920. The one exception was the post office of the Czechoslovak prefecture in Těšín, which lay in the Polish part of the town: from April 1920 it served both the prefect and the International Plebiscite Commission, and its mail was taken by car via Moravská Ostrava to the railway station at Svinov.

Sources: Lubor Kunc: Eastern Silesia 1918–1920 (Czechoslovak Specialist 5/2000), Burda Auction: Novinové (ČSR I.), Wikipedie: Seznam poštovních známek Československa 1918–1939

The Polish side wanted stamps of its own for the plebiscite area, with patriotic Cieszyn subjects such as the town's main square. The National Council of the Duchy of Cieszyn (Rada Narodowa) approved the proposal on 2 January 1920, but the Warsaw government confirmed it only on 3 February; because of the delay the Allied commission stopped the issue and ordered ordinary Polish stamps to be overprinted in the same way as the Czechoslovak ones. The ten-stamp S.O. 1920 series – five fenig and five crown values – appeared on 15 April 1920 and was valid at Polish post offices in the plebiscite area until 10 September 1920.

Sources: Lubor Kunc: Eastern Silesia 1918–1920 (Czechoslovak Specialist 5/2000), Wikipedia (pl): Historia znaczków pocztowych na ziemiach polskich, Wojtek z Roztoki: S.O. 1920

The higher, crown values of the Polish S.O. 1920 series were used at the same time as the Czechoslovak overprints, but never together: one side's stamps were not valid on the other's territory, so Polish and Czechoslovak S.O. 1920 stamps cannot be found on the same cover. In the villages awarded to Czechoslovakia by the arbitration of July 1920, the Polish stamps were valid only until 10 August 1920. Těšín itself was split by the border: the centre with the Těšín 1 post office went to Poland as Cieszyn, and the part with the railway station and the Těšín 2 post office to Czechoslovakia as Český Těšín.

Sources: Lubor Kunc: Eastern Silesia 1918–1920 (Czechoslovak Specialist 5/2000), Wikipedia (pl): Historia znaczków pocztowych na ziemiach polskich