The year was 1999, and on a late November day the volunteers at the Ningbo Charity Federation in Eastern China found a strange letter addressed to them from an individual referred to only as shun qi zi ran, translated roughly to "let nature take its course."

Inside was 50,000 Chinese RMB, or around $7,000 in remittances-payments typically sent from a person back home to their family from a foreign country.

Next year, the same letter came from ‘let nature take its course," and the year after that, and the year after that; each one filled with money.

Three weeks ago, another letter came totaling 1.08 million RMB ($150,000) across 100 different remittance certificates. It marks the fifteenth million sent to the charity-more than $2 million-across 25 years of anonymous giving.

"He sent us a letter. I remember he said in it, 'I will not do bad things and will also not speak about the good things I did. Just let nature take its course,'" Gao Peng, secretary-general of the Ningbo Charity, was quoted as saying.

"So we respected his wish and did not try to find him. We also followed his request of using his donations for education."

Mainland China banking regulations stipulate that cash transfers of over $1,500 require identification, and so the donor used remittances to circumvent the rule and maintain his anonymity.

The donations stretch back to a time when China was far poorer than it is today, with a GDP one-third that of Japan and one-ninth that of America.

Ningbo Charity has said they used the money over the years to build several schools for underprivileged children in the Province of Zhejiang.

Chinese culture is nothing if not particular, and stories of anonymous donors are not uncommon. They often trend online, in fact, and South China Morning Post referred to a story from central China's Hebei Province where a senior care home received several donations totaling around $875,000 from an "old friend."

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