In Star Wars Rebels, Rex claims he didn’t keep track of his droid kills. If that’s true, what are the hash marks on his helmet for? To confuse things even more, in a 2011 interview with IGN, Dave Filoni specifically says Rex has kill marks all over his armor. So what’s the deal?
We can only speculate, but I assume the hash marks symbolize more significant kills or missions. Rex destroys countless droids in the Clone Wars, that would be impossible to track anyway. But maybe he did keep track of tanks he single handedly took down. Or maybe they’re missions he wanted to remember. Or maybe we’re all way off base and each mark is keeping track of every time he had to cover for Anakin while he made a call to Padme.