Milton, the gun your link goes to is a Grade 2 Damascus barrel gun serial number 12249. The OP's gun is serial number 21733 and is the lowest Grade 0 with no engraving or checkering and Twist barrels. The number on the barrel flat of the OP's gun is the Order Number 12175. The serial number on the barrel should be on the side of the barrel lug.
12249 01 Grade 2, 12-gauge.jpg