Hi there,
Here's the verbiage in the French Standard again and here is the advice from Bev Davis' web site again. These are the people who have been breeding these birds longer than just about anyone and know more about them than just about anyone. Again, Bev Davis' verbiage is very important. The birds have to lay at least #4 AT SOME POINT in the lay cycle. That's all. Not much to achieve really. Both of the two main Breed Clubs in the US agree with this and so do virtually all of the other well known breeders who have contributed to developing the breed in the US.
MCF standard:
http://marans-club.perso.neuf.fr/standang.htm#standard
"Characteristics of hatching eggs
The eggs should be large, ranging in size from about 65 grams for a pullet to 70-80 grams for an adult hen.
To have a deep dark red-brown coloured shell."
And on the MCF's Brown Red Variety page they discuss the challenges of breeding the Brown Red variety. Essentially, what they are saying in the first sentence is that working on the priority of egg color caused some foundation stock to lack the proper balance of black and copper in the feather color and on the other hand, breeding for feather color only has hurt egg color in some stock.
Brown Red Variety Page:
http://marans-club.perso.neuf.fr/ncuiang.htm#NCUI
"Moreover, it is obvious that the selection of the "true" Marans, which, since the beginning of time, has the priority for the reddish-brown egg, has contributed to check the achieving of a Brown-red founders which are very correctly color-stabilized.
Conversly, there are very nice Brown-red Marans stock known as "competing" that is to say too much selected in this way but which, for lack of a sufficient plural selection, see their eggs to be too much light-colored for the breed. Be clear and precise : they are not Marans anymore ! Let's be quite clear about this : we mean genetically pure Marans
"
Bev Davis site page on True Marans:
http://bevsmarans.com/TRUE Marans.htm
"Use care when purchasing "Marans" from sources. No matter how beautiful the color of bird, if the flock is not producing #4 or better eggs at some point of the laying cycle, the birds technically DO NOT QUALIFY AS MARANS, PERIOD. (According to the French Marans standard)"