Once again a nice experiment, love your scientific and experimental approach towards honing.

Just some thoughts:
I've looked at the scratch pattern pictures but found it really hard to distinguish the different hones with the exception of the first pic being the DMT 1200 (but I could easily be wrong on this one).

Without wanting to be a pain in the ###, the scratch pattern and light contrast in the first picture is very noticeable and the others are not which is why it gives me the impression that the others are out of focus (again, I could easily be wrong).

Looking at the microscope photograph I assume it is not capable of digital imagery and had to shoot the pictures thru the eye piece.

You mentioned the consistent light angle on the subject, as for I can see the light source is attached (magic arm/ tripod?) and there for not able to move freely.
But I am wondering how you managed to achieve this with the aluminium object lying freely on the glass support of the microscope?

Due to your experiments with light you might find this interesting. Although the pics in the book are a bit old fashioned,
this is a very good, if not the best book on lighting principles there is:

Light: Science and Magic: An Introduction to Photographic Lighting

Maybe there is updated version available.