You can't. Contact the police if you believe it is stolen.
Check in between the lugs of the watch. Here's a complete guide on how to find and look up a Rolex Serial Number: http://www.bobswatches.com/rolex-serial-numbers
Check the barrel and receiver.
Check the receiver and barrel
Check the butt and crane areas ---------------------------------------------------------------------- My Redhawk's serial # is under the grips on the frame
Check under the forearm
Check the entire receiver carefully.
Check the reciept
Check the receiver and barrel.
Check on line auctions
Check the butt of the weapon.
Check the barrel and frame.
check out this link -> http://indesignsecrets.com/help-ive-lost-my-serial-number.php