The picture in the article is cropped. In the original iFixit teardown you see that the pattern is right next to a laser-engraved data matrix code [1].
The indentations probably encode some quality-control type metadata from the CNC milling machine (like the version of the plan used to mill the part). iFixit just happend to get a glider in theirs.
The indentations probably encode some quality-control type metadata from the CNC milling machine (like the version of the plan used to mill the part). iFixit just happend to get a glider in theirs.
[1] http://guide-images.ifixit.net/igi/GGjmUQwXwlrFJAUy.huge