Bob Mansfield, Apple's senior vice president of Mac and devices hardware engineering, has cashed in on $13.7 million in stock after selling 38,863 of his shares for $351.89 each, reveals a filing with the US Securities and Exchange Commission.

Mansfield, the familiar face from Apple's product videos, is not your ordinary short-seller, even though he honed the art of buying and selling stock to the perfection, according to Fortune's Philip Elmer-DeWitt.

He's known to selling shares at their peak and exercising his employee discount to buy them again when they fall.

Do that often and with enough shares, and you'll profit quite a lot.

More precisely, over the past three years Mansfield's clever buying and selling earned him a cool $37.9 million after taxes. Who said putting in long hours at Apple doesn't pay off?

Mansfield earned a BSEE degree from the University of Texas in 1982. He reports directly to Timothy Cook, Apple's operations wizard currently covering for Jobs. Prior to joining Apple in 1999, Mansfield served in executive capacities at Raycer Graphics and was a senior director at SGI, where he was overseeing the development of various microprocessor designs.

Mansfield was originally charged with Mac development and was credited with heading the team that brought you the iMac and the MacBook Air. In August 2010, he took over the position of Devices Hardware Engineering after the abrupt departure of ex-IBM executive Mark Papermaster and is now responsible for the Mac and iPhone hardware teams.

Apple regularly features Bob Mansfield and other high-ranked engineers and executives in promo footage for new gadgets.