Sharol, you will love the Marans - I really like mine and love the dark brown eggs. I had a gorgeous BCM who was unfortunately killed by the fox. She was my highest quality bird at the time - her breeding really showed. They are quiet and gentle, and really good layers. My Cuckoo Marans is in her third year of laying and still lays two out of every three days. She has always, since she started, laid two days then taken the third off. I figured that would slow down over time but she's been very consistent and still lays in that pattern now.
I've never heard of a mark on the eggs bothering them, but yes, if the eggs are easily identifiable already its not necessary to mark them. I usually mark with a sharpie, an X on one side of the egg and an O on the other, so I can easily see an identifying mark when I check. On chicken eggs that's not a problem but I did have a little issue with the duck eggs that because their surface is different, the marks got rubbed off and the ones I have marked under broodies now are so faint I really have to look closely to see them.
So closely that I gathered one by accident and brought it in and set it in the egg carton. A few days later I decided to set some of the duck eggs in the incubator and while doing that, I noticed the mark that meant I had carried in a developing egg. Darn. I decided to put it in the incubator anyway. I didn't know how long it had been out of the nest but I do know it was at least 3-4 days. I figured I didn't have much to lose putting it in the incubator, but knowing it wouldn't develop. Here's the thing. I candled a couple of days ago and it is developing! I had no idea you could interrupt incubation for DAYS and the fetus would continue to develop upon resuming incubation. I'm sure that's only the case this time of year when the days are so warm, but still, I was stunned when I candled and realized I was seeing movement in that egg. Amazing.
I wrote a couple of days ago that there were a couple of wild turkey poults hanging around but I had seen them from a distance. I now think they are juvenile ringneck pheasants! They have continued to hang around and I see them everyday when I'm out doing my chores. I think they are attracted to my flock and the prospect of free grain. Heck, I wouldn't even mind if they jumped down and got a little food - I'm just tickled to see them!