Two categories of people who clock me:
1. People in LGBT settings, where it's expected there will be transgirls, so a 5'11" girl triggers transdar.
2. Tall women who are used to looking eye-to-eye with other tall women but find they still look up at me.
It seems that someone who is suspicious will find enough strangeness (narrow hips, broader shoulders, wide chin, adams apple, craggy forehead, etc.) that they can figure it out, but unsuspicious people will generally not clock me.