The heading of this thread needed to be changed.
IF:
A person took a good counterfit chip to a slabber, I doubt they would know or care. They are grading the chip brought to them.

IF:
It is in a slab, there is every possibility that a knowledgeable chip collector could not tell it was counterfit. If he held it in his hand there is every possibility that a knowledgeable chip collector could tell it was counterfit.

You can not see the rim in a slab.

That being said, we know of no high end or low end counterfits.
There are only altered chips, fantasy, and fake chips made to fool collectors (like the official Mizpah fakes). One post here would ID any of them.
The Fremont $25 is the best I have ever seen but IT IS STILL AN ALTERED CHIP.

Greg, can you scan a few chips in your collection to the BB?