1 May 1967 - 30 June 1971
US foreign surface letter rate 13 c
Swedish foreign surface letter rate 70 öre
US handstamp shows amount to pay in US cents (normally double deficiency) and US surface letter rate.
In Sweden the indicated fraction multiplied by 70 and rounded up to nearest 5 öre was normally paid by affixing stamps on the item.

Single rate air mail letter with 10 cent. Correct rate 20 cent. Shortpaid 10 cent. US due handstamp indicates double deficiency 2x10=20 cent and surface letter rate 13 cent. The fraction 20/13 multiplied by Swedish foreign rate 70 öre = 107.69 öre ruonded up to 110 öre charged by affixing postage stamps. Originally this item was regarded as a postcard and charged 6 c double deficiency but probably as much has been written to the right of the division line the item has finally been charged at letter rate.