Wear is tricky to see. When the history of the stylus is unknown it is wise to replace the stylus rather than risk damaging the discs.
In another thread Ray Parkhurst has started showing pictures he has made using focus-stacking and very careful lighting, some of these enable wear to be seen, the thread is here viewtopic.php?f=19&t=92996
There was a stylus microscope made by SHURE long ago, model SEK2, it had two lights above the stylus, with a dual slide moving stage with fine adjustment to get the stylus centered, and zoom magnification up to 200x. They change hands on ebay rarely for a few hundred US$, but the results are inferior to focus stacking photography, which has superior depth of field.