I can tell a Maran cockerel, and hen, as there is a distinct difference in their grey feathers. Its not easy with some breeds though. If you look closely, the males comb appears sooner, although not always. Twice I have been certain I had silkie pullets and both turned into cockerels. The only sure way of knowing, is that first cock a doodle doooo........and you have that sinking feeling. Its a known fact that you always hatch more cockerels than pullet
And do not ask me why Langdon, cos I do not know!!