Hi Gav,
Talc isn't a bad idea. Check out the techniques for seeing the images on old gravestones and petroglyphs. Basically, use a non-staining fine powder that has a color in contrast to the surface, to fill in the grooves and make them more evident.
Alternatively, light the piece from a low angle, along the blade (like the setting sun), so that the shadows from any grooves or ridges stand out.
So far as the microscope goes, you want a dissecting microscope, not a compound microscope. If you can't get anything from the physicist, you can often buy one surplus for well under a thousand dollars. Or if that's too much, there are number of simple magnifiers (for jewelers, fishing fly makers and other hobbyists) which would work too.
Best,
F
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