It does look like a marans egg, although not super dark for a BC. Does the breeder have other varieties? It is possible to get the occasional clean legged bird, although not desirable here in the US.
These eggs are from French BCM's so I believe they should have feathered legs. I believe the breeder has other breeds of chickens, but only these Marans. Half were pullet eggs, and half were large eggs. This little one came from one of the pullet eggs. I don't mind a little variety. I have a pip on one of the other eggs. Day 21 isn't till tomorrow.