Field sketch of isolated plaster glyphs recovered from sanctuary panel of Temple XVIII.

First there were some original glyphs, which were later hidden by plaster, and replaced by a set of different glyphs, engraved partially in stone and partially in plaster.

http://vma.uoregon.edu/inst_doprofile.lasso?&DoWhat=d&Document=1467

http://vejprty.com/abyhelic.htm