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 entire receiver carefully.
Check under the forearm
Check the reciept
Check the butt and crane areas ---------------------------------------------------------------------- My Redhawk's serial # is under the grips on the frame
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