Showing some plant detailing obscured under green paint

[eggyk]

Maybe I have Pareidolia, but could it be the signature in the yellow, Jan Eyck of Liege? 

It's pareidolia, trust me. It happens a lot with this type of tool. When something is really there, it's really quite obvious. You will see such things all over the page, and its often deformations in the parchment, general unevenness, or simply a part where the contrast blurs into apparent patterns which aren't there.