ca April 1888 to 31 Dec 1891
US foreign surface letter rate 5 c
US Conversion rate 1 US cent = 5 goldcentimes
Swedish conversion rate 1 goldcentime = 0.80 öre for letters, 1 goldcentime=1 öre for postcards and printed matters
US marking shows the amount missing in goldcentimes.
In Sweden the indicated amount was doubled and multiplied by 0.80 for letters and 1 for postcards and printed matters. The amount due was paid by affixing postage due stamps.
Postal card with 1 cent. Correct rate 2 cent. Shortpaid 1 cent. There is no centime due value noted in the USA. However the Swedish mail know that it was half paid and charged the double of a half rate 0.5x2x10=10 öre. A correct USA due note should have been T10, which then should have been multiplied with the Swedish exchange rate for postcards, 1, which also had given 10 öre due.