Ronny,
It is certainly a close shot. I see focus fall off towards the edges. Since this is a flat object and not a three dimensional fossil, I would have expected better resolution all across the image if this were a high quality optic.
Also, this appears to be a fixed magnification 30X microscope attachment. That is way too high of a magnification for most things I photograph.
Sorry that I am so critical. That comes from being a perfectionist.
Jack