Anyone know how PCGS determines cameo on proof like coins?

I picked this up at melt, mind you when it was peak silver, and I thought it was a slam dunk for a deep cameo or cameo......of course, the graders dashed my hopes and dreams. Any opinions?

1
Comments
More than likely because of the toning. It takes away from the
“black and white “ effect needed for a cameo designation.
I was going to say if that coin was dipped you may have got the designation.
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I don't find either service consistent with this designation either. Part it I suspect is that the coin shows better contrast outside of the holder, but I've never heard anyone else say it.
Latin American Collection
It's not as Black and White as it should be...
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The toning is a deterant, jmo