I'm wondering the same about my white silkies. Since I wanted to end up with one pullet, I got 4 chicks. I also got 4 mille fleur d'Uccles, and at 3.5 weeks, I could get a good idea of who was who with them, but with those silkies, as hard as I try to scrutinize their combs and behavior, I just can't peg them. According to these factors, I might have 3 roos and one pullet! With the d'Uccles, I lucked out with 2 roos and 2 pullets. Even on the d'Uccles, you can feel the very beginnings of spurs on their legs. Not so much with the silkies, but that's one thing I will keep a keen eye on- the development of those spurs.
Thanks! Good to know! Maybe if my BlueEgg (the chicken egg that Birda hatched) turns out to be a hen (s/he's back at the farm where I got the egg), I can ask for her back. The lady said she has too many birds anyway... I was kind of heartbroken thinking BlueEgg was a cockerel, so it would be grand if I turned out to be wrong about that one!