International letter with perfin “S.L.S.” in the stamps. The letter is franked correctly with 20 + 10 ører = 30 øre, which was the rate for international letters 20 to 40 g in the period from October 1st 1907 to January 31th 1921. The stamps are cancelled April 17th 1915 with Bro III Odense – Svendborg (railway). This is the only known prove of S.L.S. perfin and also the earliest known use of S.L.S.