The edges look set and slightly pulled away from the pan
The center is no longer jiggly
A toothpick inserted in the center comes out with moist crumbs, not wet batter
The top looks matte and may have a thin crackly surface
The brownies feel firm around the edges but still slightly soft in the middle
The internal temperature is about 200°F to 205°F
The pan no longer looks glossy with raw batter in the center
The brownies have risen and then settled slightly from the oven