Registered letter sent by the member of CIS commission, Oscar von Sydow, Chief of Göteborg from Flensburg 1 April 1920 to Göteborg, Sweden. Franked with CIS overprint 2½ Pf, 7½ pf and 20 Pf tied by datestamp FLENSBURG 1.4.20 9-10N. Registration label ‘R Flensburg 1. NO. 119’ and cachet of ‘COMMISSION INTERNATIONALE / SLESVIG’, letter inside with official letter header of the commission.