Facebook (NASDAQ:FB) COO Sheryl Sandberg last week sold approximately 2.37 million Facebook shares at an average weighted selling price of about $38 a share, according to a recent SEC filing.

The sale of stock by the former Google executive was made under a trading plan from July 2012. It came as the stock finally climbed above its IPO price of $38. Facebook stock was trading at $24.71 a share just a month ago, but has risen dramatically since announcing surprisingly strong earnings on July 24.

The proceeds of the four series of transactions enacted on behalf of Sandberg on Aug. 7 are approximately $91 million based on average weighted selling prices ranging from $38.3826 to $38.925. The series of stock sales included 2,274,095 shares, another of 91,500 shares, plus smaller sales of 6,496 and 200 shares.

The SEC Form 4 filing states that Sandberg's trading plan implemented last year was "pursuant to a Rule 10b5-1 trading plan." A 10b5-1 plan is a regulatory option sometimes utilized by company insiders to help avoid concerns regarding improper insider trading. Bloomberg reports that Sandberg still owns more than 14 million Facebook shares. Facebook's market cap is over $90 billion.