Recently we purchased 20 blue copper maran hatchlings. They were actually a mix of quite a few different types of maran. From black copper marans, to blue and even some cuckoo marans, We even got a white one. Which i believe is when a blue and a blue maran have babies.
Marans have the some of the lowest lay rate of most breeds. Since I new this going in I am expecting some quality eggs. We currently have mottled javas and those are also slow layers, maybe 1 per 2.5 days. However they have really large yolks and are excellent.
Some speculate that selecting for dark eggs has reduced the lay rate because dark eggs pass thru the oviduct more slowly receiving additional coats of color. Brown egg color is controlled by at least 14 genes and is not well understood. If it were as simple as only hatching the dark eggs, everyone would have a good line within one generation. If you are simply interested in dark brown eggs, you should also consider the Welsummer.
I will add some pics to our gallery soon