My mistake on the "not even digits" with regards to code for this lens, just noticed that there is a 10-digit code printed quite faintly above the Canon Inc words, the same number as in the barcode on the box.. Besides this, there is no indication that it is a version 2 but the 5D Mk III confirms it when u go into the menu. So I guess if one is buying a second hand copy of the MK2 24-70mm, one needs to check that this code is there and not the presence of the U-series code. I hv no version 1 to compare but the AF is really fast.