Garman Airmail Letter Rate

In the 1800's, the UPU standardized stamp colors with green for domestic post card, red for international post card and domestic letter, and blue for international letter. For the US and Canada that was 1,2 and 5 cents. For Switzerland and Austria it was 5, 10 and 25, but for Germany is appears to be 5, 10, and 20. Why the difference? Other countries are international letter 5 times post card rate, why is Germany different, or am I missing something?

The UPU green color is not for domestic postcards, it is for first rate international printed matters. Regarding the rates they should be set at 5, 10 and 25 (gold)centimes and each country had an exchange factor to the gold franc. When converting the rates it was allowed to have a small difference from these rates. The conversion rates for countries like Switzerland, Italy and France were 1 to 1 so here it was easy. The rates became 5, 10 and 25. For Germany the exchange rate was 1 to 0.9 so here an exact rate should be 4.5, 9 and 22.5 but the Germans used the right to make a small difference and set the rates to 5, 10 and 20 pf. Sweden had the exchange rate 1 to 0.8 so here the exact rate should be 4, 8 and 20 but they set the rates at 5, 10 and 20.

Don't know.

Thanks a lot. Mystery solved