I think this has to do with the waffle pattern on the chip. If you look at the chips you can see some where the waffles make a distinct checker pattern and then as they move closer together. There are some that give the impression that the letters are floating with the way the background pattern occurs. As stated in other threads I found in a rack that every chip has a small difference in the way the background of the inlay looks and I picked 4-5 "interesting" ones for me and kept one of them in my collection. It sorta looks like a hologram (and maybe that was the intention or a interesting side-effect).