Here are three close-ups (from the EIII datafile) that show the pattern very clearly. It's obviously the work of a practiced hand...and more "regular" in some ways than my random squiggles. Note, in the third photo, how the worker has gone "back and forth" on part of the area under the wing. This was practical work...not art.

My problem was after studying Arabic in college and spending 12 years in the Arabian Gulf, my "random squiggles" were starting to look like Arabic words!