I have been lucky enough to obtain three hens from a really dark egg laying strain and an unrelated cockerel from show stock. They are laying well and eggs will soon go in the incubator.
Black copper marans are supposed to lay the darkest eggs of the marans. They are certainly darker than my blue marans hen (eggs from her can be included too if required).
Marans as a breed originated in France and were developed from local feral chickens which were thought to have descended from fighting game chickens from Indonesia and India. Croad langshans were added to improve the breed and now it is dual purpose for eggs and meat.
My black copper marans hens all have some feathering on their legs, as does the blue hen. They are calm, friendly hens and like to forage through the compost heap.