The "DOT" symbol certifies the tire manufacturer's compliance with the U.S. Department of Transportation tire safety standards. The DOT serial number is located on the lower sidewall of the tire, on one side only. Below is a description of the serial number. 

Serial Number = DOT NJ HR 2AE2 2510

2510 = The Date of Manufacturer. (Made in the 25th week of 2010.)

2AE2 = The Tire Type Code (This section of the code is not required and may not be present on all tires.)

HR = The Tire Size Code Number.

NJ = The Manufacturer's Plant Identification Code

DOT = Certifies the tire manufacturer's compliance with U.S. Department of Transportation tire safety standards.