Someone else did it and claimed they were because one of the two are gold based which is another version of sex linked but if have to find the post he posted basically they look like this
Sorry I don't have a younger picture nor do I understand how it's dark brownish/blackish butt and not red but there you go
I think they were probably buff Orpington rooster over barred Plymouth rocks. That is the very colorization that that mating turns out.
Read the sexlink thread and find the matings for Sexlinks. They have chart posted I think right on the first or second post.
