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.
Double rate air mail letter with 30 cent. Correct rate 40 cent. Shortpaid 10 cent. US due handstamp indicates double deficiency 2x10=20 cent and surface letter rate 13 cent. Amount due in Sweden, 20/13 multiplied by Swedish foreign letter rate 70 öre = 107.69 rounded down to 110 öre paid by affixing postage stamps.