1 May 1975 - 31 Dec 1975
US foreign surface letter rate 18 c
Swedish foreign surface letter rate 110 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 110 and rounded up to nearest 5 öre was normally paid by affixing stamps on the item.

Unfranked post card. Correct rate 12 cent. Shortpaid 12 cent. US due handstamp indicates double deficiency 24 cent and foreign letter rate 18 cent. Swedish due should have been 24/18 of 110 = 146.67 öre rounded up to 150 öre but no due seems to have been charged in Sweden.