White Wyandotte, Cornish X, or something else?

[cejunes]

I'm really confused on this girl. I got her from a small local feed store and she was the only white (yellow at the time) chick in the store. The lady I got them from said they were all supposed to be single breed chickens but I'm not sure what she is. She is 5 months old and is laying brown eggs for me. White is the only color in her feathers. There is not even a hint of another color. Her legs are yellow and she is a good size pullet. She currently weighs about 7-8lbs. Please help!

Her egg is the darker of the two pictured below...

 

[cannoteatchickensanymore]

She is White Rock. A single comb and brown eggs suggest that.

 

[cejunes]

That's a breed that I hadn't even thought of. When I think of rocks, I think of Partridge and Barred. I guess that would make sense though. My only thought on that one though, is why is she so big?

 

[Chickanmanfromarkansas]

cannoteatchickensanymore
She is White Rock. A single comb and brown

Agreed. Looks like my white Rock pullets.​