I don't know what hatchery they came from. I got them from Atwood's Farm Supply. I am not sure about the dark cornish...her legs don't seem to be out of proportion to her body like the cornish I've seen pictures of. And her feathers seem fluffy, not "tight" like the description. I did see some young wyandottes that looked like her. I guess I'll have to wait til she is fully feathered.
As far as RTA or "Roger" I agree that she is probably a pullet, which works out fine for me! LOL! I do think she has the body style of an OEGB, so that is a definite possibility. I think the Columbian pattern is a definite possibility. I haven't been able to see a pic of the backs of the Columbian pattern, so I can't really see a splash pattern like (s)he has. But, I know things can change until the first big moult.
Thanks for the input! If anyone has any other ideas, I'd love to hear them!
Shelly