Facebook Inc. has estimated its market value to be worth about $3.7 billion according to a lawsuit brought by former classmates of CEO Mark Zuckerberg last summer.

The information comes from the Associated Press in a report that explains how it cracked the electronic versions of blacked-out court documents. Facebook's appraisal, which was mentioned in a June hearing as a long court battle with ConnectU was concluding.

ConnectU sued Facebook founder Mark Zuckerberg for stealing the social networking concept from three classmates.

The appraisal was conducted after it sold a 1.6 percent stake to Microsoft that implied a value of $15 billion for the social networking outfit.

Facebook, the largest online social network, made the assessment after making a deal with Microsoft in October 2007. As part of a broader advertising partnership with Microsoft, Facebook agreed to sell a 1.6 percent stake to the software maker for $240 million.

The settlement called for $20 million in cash and 1,253,326 shares of common stock; by Facebook's internal math, the common stock was worth $11 million compared with $45 million at the Microsoft value, according to AP. That would make the settlement worth anywhere from $31 million to $65 million.

The Microsoft-Facebook deal was similar to Google's $1 billion payment for 5 percent of AOL to help the Time Warner unit get a value of $20 billion. Google went on to write that deal down by some two-thirds last month, then acted on a clause allowing it to demand repayment at fair market value or for an IPO.