Cuckoo Marans look similar to barred rocks, but have a messier, darker sort of striping. They have white/pinkish feet. They can have light feathering on the outside of the leg (French lines) or not (English lines). They have straight combs.
It's unlikely that you stumbled on good Marans without knowing it, but stranger things have happened I suppose. They're still relatively valuable and not SUPER common, but lots of us on here have them.
Post some picture and I'm sure you'll get plenty of opinions on what you have.
I stumbled on a marans at the Tracktor Supply Store here in South Texas, just outside San Antonio. I asked for 2 Ameruacanas and 2 GLW. I got her and 1 Ameruacana. She is the most timid chicken in the flock.
I don't rcall seeing a sign that said Marans, but I could be wrong.