Broody hen sitting on others eggs

[CreamLegbar]

I have a hen sitting three days in one of my nesting boxes. I also have 5 other hens that are laying eggs using the box along side her. I know I should mark the eggs she started with, but missed one opportunity when she left the nest for a few hours. What is the best way to get to the eggs to mark them? Can I just use a permanent marker to mark them? How long can the eggs go without her sitting on them (outside temp 50-60 deg F). She looks like she is trying to cover a lot of eggs. I had a similar experience last year when finally the hen got off the eggs at about 14 days. There were more than a dozen and I didn't know old they were. Should I take the other eggs and put them in the incubator?

 

[nuthatched]

A sharpie is fine

 

[CreamLegbar]

Broody hen finally gave up. She had a large number of eggs underneath her. It took a day or so for her to stop laying on other eggs. Now she seems to be slowly joining the flock although she has been reminded of her place in the pecking order. She is the youngest of the hens, actually one of which is her mother. Finally able to get some normalcy and able to collect eggs knowing which are fresh. The one thing I learned was to be more aggressive in marking eggs as soon as she went broody. That way I could remove the newer eggs as the others laid them, but I waited too late to start. End result was a lot of discarded eggs and no new chicks.