From looking at large stacks of product boxes I can say there is a unique box identifier on the box label for performers, kettles, WSMs and joes.
In bold letters at the bottom of the label above the box dimensions, it looks something like:
HDExxxxxx yyyy(x's are integers as are y's, y's appear to be a lot code)
This number corresponds to performer serial number, but for kettles WSMs and joes only the two digit date code portion is stamped on the unit as mentioned above.
It seems strange to me to go to the trouble of creating unique box IDs but not serialize the product. I'm sure they have their reasons.