The Temple of Saturn in the Roman Forum.
It looks like there were letters, likely of precious metal, fitted into the stone, held in place by pegs, the holes for which remain.
The vacant letter shapes have a very slight glyphic quality, but are otherwise remarkably monoline and “geometric”.
I doubt the metal letters would have imitated the v-shaped concavity of the usual incised method, as that would have weakened the pegs’ attachment. Would the finish have been flush? Who knows, it may even have been raised and bevelled.