Not a Jersey Giant because they don't have white earlobes...I agree could be a mix of Jersey Giant, however not sex-liked as the coloring is the wrong way for that (the females of black sex-links will be black usually with red bleed through while the males will be barred as typically the black sex linking is a red based roo over a barred female)
The white earlobes on a black bird could indicate Minorca.The Minorca does not carry the size or weight of a Jersey Giant, but it is the largest of the Mediterranean class. Without seeing the bird in person, I have no idea how large you mean when you say large....and it is possible that chick is simply older than the rest of the chicks that were sent.
Not sure what the brown is about though as that would not fit Minorca...it could be transition feathers that will drop away, but I can't think of a very large brown/black bird with white ear lobe. Interesting to see what others say.
Look through the list of specialty breeds on the hatchery website. That might give you an idea.
He may be a packing peanut which means he is probably an "oops" mix thrown in to keep your order warm in transit.
I hadn't even thought about it being a Black Copper Marans. This one doesn't have feathered legs, but I think I have heard that hatchery quality Marans don't have feathered legs. Is that correct? And do they have white earlobes?
BCM don't have white ear lobes. Wrong leg color too...BCM are more slate grey not dark black (SOP is light to mid slate with pink showing in between scales). There are both feathered and non leg feathered, depending on whether American style or French (french is feathered...outside leg down outside toe)... however this is not a BCM imho.
I think it is a Jersey mix...unless someone can come up with a breed with white earlobes, black legs, yellow feet pads(?), mostly black with brown hackles.