When I purchased the older one it was listed as a Cuckoo Maran. When I purchased the younger one it was listed as a Barred Plymouth Rock. Both were purchased as little chicks, just days old. What do you think?
I think they got it right. For comparison, here are a couple pictures of mature hens.
The Cuckoo Maran View attachment 1884395
The Plymouth Barred Rock View attachment 1884396
What I clearly see is that the Plymouth BR has much crisper black and white markings compared to the Maran which has a softer black and white pattern. Also, as mentioned, the Plymouth BR has yellow legs and the Maran the white-pink legs. The pictures you uploaded of the younger chicks seem to fit the pattern of the older hens, so I think they got it right.