Small update,
after performed lapping of stone one I have notices small cranny of (what I think is) copper. You might notice this on some of the pictures. I try hone razor over this cranny and I can tell that in some point edge of the razor is hitting something different than stone itself. Funny thing is that this was not present before I start lapping. After I have removed stone surface this cranny come to picture. I guess I still have some stone left to be used of flip stone and execute lapping of other side:-)