Confronted with a plunge in its stock markets last year, China's central bank swiftly reached out to the U.S. Federal Reserve, asking it to share its play book for dealing with Wall Street's "Black Monday" crash of 1987.

The request came in a July 27 email from a People's Bank of China official with a subject line: "Your urgent assistance is greatly appreciated!"

In a message to a senior Fed staffer, the PBOC's New York-based chief representative for the Americas, Song Xiangyan, pointed to the day's 8.5 percent drop in Chinese stocks and said "my Governor would like to draw from your good experience."

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It is not known whether the PBOC had contacted the Fed to deal with previous incidents of market turmoil. The Chinese central bank and the Fed had no comment when reached by Reuters.

In a Reuters analysis last year, Fed insiders, former Fed employees and economists said that there was no official hotline between the PBOC and the Fed and that the Chinese were often reluctant to engage at international meetings.

The Chinese market crash triggered steep declines across global financial markets and within a few hours the Fed sent China's central bank a trove of publicly-available documents detailing the U.S. central bank's actions in 1987.

Fed policymakers started a two-day policy meeting the next day and took note of China's stock sell-off, according the meeting's minutes. Several said a Chinese economic slowdown could weigh on America.

Financial market contagion from China was one of the reasons cited by the Fed in September when it put off a rate hike that many analysts had expected, a sign of how important China has become both as an industrial powerhouse and as a financial market.

NO SECRETS

The messages, which Reuters obtained through an Freedom of Information Act request, show how alarmed Beijing has become over the deepening financial turmoil and offer a rare insight into one of the least understood major central banks.

The exchanges also show that while the two central banks have a collegial relationship, they might not share secrets even during a crisis.