Lots of trans people look perfectly 'normal'
Everybody looks 'normal' if you aren't a bigot but you can tell some people have changed their gender or the appearance of their gender either by way of dress and mannerisms or with more involved methods. More than once on the job someone has mentioned that they once lived with a different gender and other people who have met that person and talked to that person before are just floored by the revelation. A revelation seemed pretty apparent to me.
To be honest I bet I haven't had many false positives. I don't know until I've heard from the horses mouth or at least from good authority. I've had my suspicions confirmed more than a few times. I'm fine with ambiguity, it doesn't really matter, people should be honored for who they are and want to be. I'm sure that there have been many, many people who I never had a clue about. I wrote a big stream of consciousness reply but I don't know if I'll post it. Trying to buy my first house this week and I'm a ball of stress. My mortgage is falling apart and my guts are in knots. Went out saw some bands and had some beers to blow off some steam tonight afraid to offend a bit tipsy and generally feeling unsure and vulnerable this week. I'll give it a read tomorrow, it's only half on topic, maybe an edit maybe let it rip or let it die.