Factory cuts vs trimming

[Bigdaddy]

One would think that with a high enough magnification, identifying trimmed cards could be detected, at least to a high degree. Looking at any given edge, I envision differences in color (due to accumulated dirt, oil, etc.) from handling the cards for many years, indentations, fiber orientation, etc of a card that was cut 50 or more years ago to one that was cut in the recent past, by most probably a different method.

What am I missing here? A grader would not have to look at all cards, but a higher cost to evaluate a more expensive card at a higher grade would seem to require more diligent methods of examination, including high resolution images of the edges and surface.