As a result of the Versailles treaty, it was decided that two referendums (Plebiscites) were to be held in the northern part of Slesvig to determine the nationality of the region. The referendums were in held in Zone 1 (Sønderjylland) and Zone 2 which was an area in a belt immediately south of the current border including Flensburg. A planned referendum, further south in Zone 3 was cancelled.
In order to govern the referendums, an international commission was seated in hotel Flensburger Hof, Flensburg. The Commission Internationale de Surveillance du Plebiscite Slesvig (CIS) also governed the mail service in the referendum period.
The members of the commission were:
Oscar von Sydow (Sweden)
Thomas Heftye (Norway)
Paul Claudel (France)
Sir Charles Marling (UK), commission president.
Charles Brudenell-Bruce (UK) was the General Secretary of the commission.
It was planned that USA should also be represented with a member in the commission, but that seat was never taken, as USA never ratified the Versailles treaty.
Cover sent to commission member Oscar von Sydow (Sweden, Swedish Primeminister 1921).Except Brudenell-Bruce, the commission left Flensburg in April 1920, when the elections were completed. The General Secretary stayed until summer 1920, along with all the administrative staff in the C.I.S. HQ in Flensburger Hof.
Only 17 of the red 10 Mark-issue was ever used. I assume most, if not all, were used on similar foreign REC letters to commission members. It is notable, that the CIS-issues were only available for use by the entire C.I.S.staff until beginning of February, thus below letter is sent from the General Secreatary’s office,