Final notes, some of the etchings i got were etched longer than another batch. The less etched batch was much easier to work with but I can't help anyone one identifying them, my best guess is the the older ones were etched more than the newer batches, for whatever its worth, they are not dated other than their original desisgn. It does make a big difference in the install process. I got 3 packs and two were thin and one thicker, thinking the newer was thicker. HTH