Description: Registered First Day Cover: ZAGREB - MARINPOST 3917 12.10. 1943 (Swedish military address !!) correctly franked with commemorative exhibition stamp of KN 18 + 9.00. (KN 5.00 for foreign mail, KN 9.00 for registration and KN 4.00 air surcharge). German censor and Swedish registration numeral to obverse. Rare destination and unusual address. Very fine.