Envious.67 here
We may get down that low at 5AM in about a week.
Last time I tried to give blood they asked me my gender; ticked me off so much I walked out, after telling the interviewer that if she couldn't tell by looking that the 70 year old man sitting 3 ft from her was a male, then she didn't need my blood.
That's a good one. I have seen some that were hard to tell.
I think a more discrete way to do it would be to have people fill out their own forms.