Focus Issue

I think pepactanius has probably nailed the issue. Your iPhone sensor is so small it will have a much deeper dof than your canon(for the same field of view).

Looks to me that the top photo is better focused at the left, and as you move to the right, it becomes out of focus. Leeds me to think that you need to check the alignment of the camera with the coin?

Stereo microscopes like the AmScope and the Bausch & Lomb were designed to have a fairly small NA (aperture). This allows you to view objects with good depth of field and a reasonable level of resolution. It is also critical for stereo viewing since the focal plane is always a little tilted, with optics from one eye tilting one way, and the other eye tilting opposite. The small NA means there is a lot of diffraction in the image, so these microscopes are always going to be strongly diffraction-limited. This means the fuzziness you're seeing in these images is most likely due to diffraction, not focus, though diffraction does make it harder to find critical focus since the image is just a little fuzzy across a wide depth of field. Focus stacking can help to eliminate the focus problem due to tilt, but the end result will still lack clarity, since there is not a narrow range of sharp focus, but a wide range of fuzzy focus. This is also the case with most all USB microscopes. Their optics are optimized for good depth of field with minimally-acceptable sharpness.

Dave M tell us more please.... My camera is absent an anti aliasing filter so I don't have to contend with such effects...although on rare occasions I have been frustrated by Moire( that an anti aliasing filter is designed to prevent). I tend not to think about anti aliasing effects but it would be nice to know more

DaveM-your sharpened image does look much better. I will try to play with the originals later. Not sure of the model of my AmScope, but it was not one of the cheaper ones. My camera is inserted into one of the eye pieces rather than the port for the camera. I have not been able to get close to the shots from the camera port. I am not sure if this makes a difference since the camera port is perpendicular to the fields and the eye port is angled which might cause some of the distortion at such magnification. Still haven't figured out which rpm this one either. Either way, I feel more confident that I can produce better images after all the help, comments. Thanks!