This is a piece that illustrates that Griswold initially used the term "Dutch Oven" before "Tite-Top Baster", but then at some point returned to DO, which is how later TM pieces are seen marked. What those marks are is uncertain. Not having encountered them before, I would tend to think they are an artifact of the casting or finishing process of this one particular pot. The pot would have been clamped to a machine that spun it in order to polish grind the inside. Perhaps it wasn't properly secured, or?