It can't be a Wyandotte. They have Rose combs. This chick has a single.
I know that's how generally its supposed to go, but if they are from a hatchery sometimes if they aren't as purely bred they can have different combs. I have three SLW from TSC, two of them have a rose comb, one of them has a single comb. Which I don't mind because I didn't get them for breeding purposes, just because they are cute and I think they are pretty and I love them.

First one is a Black Sexlink pullet. Second one your going to have to wait longer. Solid black birds are very difficult to determine breed until they are much older.
You think she could be a black sex link? Mine didn't look at all like that when they were little. I'm not saying you're wrong, I do find that interesting though. I've never seen one with that much gold on the back