Next Experiment: Magnifying Filters

I agree, they do look pretty sharp.

Do you have a feel for how the filters work compared to non-filter photograph that is magnified? It would be nice to see side-by-side photos, one magnified and one using the filter, to compare the level of detail to determine the effectiveness of the filter.

Use a smaller aperture (higher f-number) to get more depth of field and reduce your focusing issues for the not-quite-parallel coin. To compensate for less light hitting the sensor, use a slower shutter speed. I am assuming you are using some sort of stabilization like a tripod or other mount. Use the two-second timer to avoid camera shake from pushing the shutter button with the longer exposure. Looks like it could be a promising setup