1 Jan 1966 to 31 Dec 1966
US foreign surface letter rate 11 c
Swedish foreign surface letter rate 60 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 60 and rounded up to nearest 5 öre was normally paid by affixing stamps on the item.
Second rate air mail letter with 24 cent. Correct rate 30 cent. Shortpaid 6 cent. US due handstamp indicates double deficiency 2x6=12 cent and foreign letter rate 11 cent. In Sweden 12/11 of foreign letter rate 60 öre = 65.45 öre rounded up to 65 öre should have been charged, but it looks as no due has been charged.