Here's the Oldest Engraving EVER. Made 430,000 to 540,000 Years Ago.

Always interesting seeing things like this come out. It could have been done by scratching some kind of marks in the shell, or it could have been done naturally by a rock in the sea, like some of you have said.
The thing is, we don't know for sure what did this.
I like the idea that it was scratched on the shell intentionally to maybe show a small map or a couple letters.

Interesting.