Upload & Sell: Off
The box...if serial #'s match (5yr logo), on some of the better glass serial #'s start with USxxxxx that might be an indication.
My 85 f1.4 and 14-24 are like that. What's a 'monkey know, Den
There's a site with serial #'s somewhere with yr of manufacture...perhaps info available there.
Actually, it's not better glass, it's newer glass.
For all newer lenses, the serial number starts with US if it's a US lens.
Unfortunately, it's not entirely clear how new a lens has to be (I believe that all AF-S and VR lenses are new enough; beyond that, I'm not so sure).