Thread: Brass issue?

Simply looks like an end of sizing mark to me.

If you're ever suspicious of pending separation, straighten out a paper clip then bend the last 3-4mm to a right angle after pointing it slightly. Feel down inside the case wall til you hit the bottom. A thinned portion will have increased friction and if it's very near separation, you'll feel a definite depression. Practice on new and old cases and you'll soon get the idea