Found this one. I soaked it in acetone, distilled water. Nothing happened. It looked like glue, or ink, but it's raised, and did not dissolve. On the far left bays the copper looks like doubled columns.
I soaked it in lighter fluid, then I soaked it in a new "California solvent" that's supposed to be "not unlike" Xylene. It's less blue now and I can see more clearly the marks inside the bays. Maybe I'll warm it up in some soapy water next.
Mike that's what I thought till he said they were raised . To me the pics look like they took a small round dremel cutter and cut the center of the affected bays out .
Only the edges of the grooves are raised as the result of metal displacement. The floor is recessed. Since they're colored blue, I suspect the tip of a fine ballpoint pen was used.
Someone must have been pretty bored, or they were trying to set me up.. lol It would be hard but not impossible to keep the pen just in the bays. Thanks everyone