Imaging 0.7mm high letters

With the same resolution as before (50μm) I scanned the smallest details I could find on the NZ 10c coin: the letters 'IRB' found just above the year numbers and so small most people don't know they are there. I misplaced the probe a bit and only got the first part of the 'I' but the results are clear enough. It's reaching the limits of the robust probe tip:

This is what the original looks like, shown on the stage with my horribly clunky probe below it. The letters approximately protrude 40μm and are 0.7mm high, or for those used to colonial measurements, just less than half the width of a piece of printer filament:

With the previous scan of the 'A', the xy slope adjustment was (0.2,-0.06) and for the 'IRB' scan, (-0.018,0.033) so it is fairly clear that the slope changes drastically depending on where on the stage the probe is. Unfortunately I did a demo to my brother-in-law just before making the scan and lost my zero, so I don't know what point the probe started from.

During the demo scanning process, the coiled copper grounding probe lost its spring and would not maintain contact, so I affixed a little PET plastic arm with a nut to ensure downward pressure. I kept nudging the coin around while putting the ground probe on, and I'm afraid some duct tape was deployed for stabilization...