Is there a special name for a corner brace which has the countersink on opposite sides? That being that on one leg of the "L" the countersink is on the side pointing out of the angle, where on the other leg it's pointing in? While searching I've only been able to find corner braces with the countersink on the inside of the "L", and I have a feeling it may just not be called a corner brace in other situations (as you probably wouldn't place it in a corner with such a countersink).
I'm going to guess, but it might be an 'outside corner bracket'? You could modify a standard corner brackets countersunk openings by using a countersunk bit on the reverse-side of the bracket.