I learned to do 3-turns and brackets in my figure-skating days, but I never learned counters or rockers.
Now, I cannot for the life of me tell a counter from a rocker.
I can distinguish both of them from a bracket and a 3-turn, no problem. I can see a turn and think, 'oh, that's the familiar one, which is a bracket' or 'oh, that's the unfamiliar one'. Sure. Easy.
But which of the two unfamiliar ones it is remains impossible.