Paint in EAS block?

Having stripped down my old EAS valve block yesterday I discovered what appears to be yellow marker paint in two of the non-return valve recess's which would presumably have effected their operation, anyone any ideas why this might have been done?

part from a scrap yard, they often mark items so do people on fleebay!

Yeah on the outside, but why dismantle and put it in bore of valve??

i dont understand where it is, but could it be any form of grease?

maybe its something thats melted in there or could it have got in somewhere?

Are you sure it isnt loctite thread locker or sealer?

Could be! question is why...... this was a working valve block when it came in the car, I've only swapped it out to refurb it, after problems that appear to have been mainly compressor related. Why gunge up one valve with anything at all??? It wasn't as if it was somewhere it could have seeped from a thread, it must have been done deliberately.

its not bits off the compressor piston seal is it?