Canon date code??
All Canon lenses come out of the same factory irrespective of whether they are sold as "US" or "grey market". This refers only to the method of importing the lens, not to any difference in the lens itself.
Not sure about the IS version but on my 70-200/4L the date code is very small and is embossed into the (very thin) black baffle at the rear of the lens. It will be six letters starting with a "U".
Some more on date codes:
|Arch-itecture by Nilesh Trivedi|
from Random Items - Challenge #30
|Rocky Mountain Elk by evancj|
from Odds are...