What breed is my little possible substitute?

[Pyxis]

Well, I just got some chicks in from Ideal, and along with my bantams I had ordered six black sex links. Sure enough, open the box and six little black peeps are running around with the tiny ones. However, I looked closer, and one was not like the others. Where the others are all black and their feathers have started coming in all black, this one is black with a brown face and belly, and its feathers are coming in in a dark brown striped with lighter brown. Is this just a color variation of black sex links, or did they run of the sex link pullets and substitute another breed? I'll get some pictures of her up in a little bit. Letting her settle in some before I go after her with the flashing box

Edit: Here she is:

 

[Gallusfarm]

Probably a Partridge Rock. Seems like they are a pretty common mystery chick this year. It will be a beautiful bird.

 

[Pyxis]

Thanks! I know Ideal does have partridge rocks, but they were sold out. Maybe they had an extra and gave her to me in place of a sex link they didn't have. Looking forward to seeing how pretty she is when she grows!