I do not have marans, but I do have olive eggers. I just bought a 2500 LED rechargeable from Walmart(Ozark) and can see into my olive eggs. I'll try for a picture but it's still barely there for the naked eye but I could see the spot/peanut and veins.
It felt warm if I left egg on for a few minutes but nothing overly hot as I did have my hand around it.
Have used 100lm pen light, on lighter EE greens. 300lm Rural King, and 600, although I have not tested that one yet on these new eggs. +Will do this weekend when I candle again.
Pic shows: EE1 and EE 2, hopefully you can see the labels