Bad news- they're not even marans. Not copper- that's black and brown coloring. Those birds are showing cuckoo/barring. Their yellow legs and beaks with really poor barring indicate they are most likely mixes- as in breed mixes not marans color mixes. Most likely barred rock with something black- sex link or...? Bit early to be sure, however the one shown by itself is already so heavy and thick looking, it may be a male.
edit- sorry, looked at enlargement of the last pic- that one is showing black copper coloring. It may be a copper marans- can't see much of it, however them selling you the other one as bcm would make me worry a little bit. Honest mistakes do happen though...