There is a model identifier, it's just hidden in the system profiler (Mid 2011 air is MacBookAir4,2)
Re:Apple releases Ipad 3
by WiseWeasel on Wednesday March 07, 2012 @03:42PM
(#3677094)
I guess it helps that the iPad is on a yearly release schedule, as opposed to their Mac products.
Although admittedly we already have that with most of their other devices ("do i have an early 2011 MB or was it the mid-2010?") and it's not like other vendors are much better in this regard.