Perhaps there is a better analysis available, but the lines of the phallus appear to me to have been cut by the same author of the letters in the words.

Besides that, having dated an archeology student who left their interesting books around, I seem to remember there being a standard for identifying the cut of these objects. Perhaps it was more easily verified than we might think.

Somebody had to be really hard-core to do it in stone.

(Apologies for the doubles-entendres! Really, they write themselves.)