Indeed, it is sometimes used to check the approximate manufactured dates because certain batches of certain lens may have some QC-related problems, etc, etc.
Any brudders/ sistas like to share where I can find such markings? So far, I've only been busy exploring my cam's features, capabilities, and of cos my humble techniques...
Not only knowing the lens code will determine if it's a stolen copy, it also determines the age of the lens. For example for Canon's L lenses, a code say UU0612, 'UU' is for year 2006 of manufacture and '0612' is manufactured on June 12th. So for this year, the code should be 'UV'.