Sweden. Foreign-related cover. Papal state. Unpaid cover sent from STOCKHOLM 15.4.1857, during the sk bco stamp period, via Hamburg to Rome. Cancellations AUS SCHWEDEN, KS&NPA HAMBURG 20.4.1857, HAMBURG 20.4 and ROMA 28.APR.57. Opened up for display. Postage due notation "26" (biacci).