If they were Black Copper Marans the hens would be black and the cockerels would be single barred.
If it were a black copper hen the pullets wold not be barred, but rather solid black with copper.
If it's a legbar rooster over BCM hens the female offspring will be barred.
The difference in breeding to a BCM and a cuckoo is that with the cuckoo the male offspring will be double factor barred.
With the OP having a cuckoo hen there may be larger head spots on the males because of the DF barring.
It would also be obvious if you hatch any pure CCL because they would be chipmunk striped.