Have the MacBooks Pro in 2011 and 2012 still shipped with installation disks?
Mac OS X 10.7 Lion was released to manufacturing on July 1, 2011 and was the first Mac OS that was not made available on optical media. I believe that the last MBP to ship with optical media were the Early 2011 models which were introduced in February 2011 shipping with Mac OS X 10.6.6 meaning that the Late 2011 MBP introduced October 2011 and shipping with Mac OS X 10.7.2 would have been the first to ship without optical media.