When we could not find the answer directly from Chinese rates, we had to try the foreign offices’ rates for possible explanations. I checked the Indo-Chinese postal rates and found that from Feb. 16, 1879 to Dec. 31, 1898 the rate for a letter up to 10 grams was 25 centimes; from Jan.1, 1899 the rate was reduced to 15 centimes; and from 1907 to 1919 the rate was further reduced to 10 centimes. Most importantly, these rates were unified rates, which means that the same rates were applicable to domestic and international destinations, French colonies and non-French colonies – there was one rate for everywhere. The cover in question was mailed in March 1902 and therefore, the 15 centimes was the applicable rate for Indo-Chinese Post Office. 15 centimes was equivalent to 6 cents of the silver dollar. I assume that the sender of this mail knew of the lower Indo-Chinese rate and the Chinese dollar equivalent amount, then took advantage of the lower rate and saved 40% of the postage. Although I have not found confirmation of this in writing yet, there should be existing documentation referring to this. For the time being, we are assuming that since the sender had already paid 6 cents in Chinese stamp (equivalent to 15 centimes), the IPO would not lose money on the item, and it was therefore an acceptable practice.