How do you object to someone who sells you something that they say is in "really good condition" when you do not know what that means?

Well the question assumes that you don't have an opportunity to see the chip and decide for yourself what condition it is in. Among deals with Club members that problem is solved by the Code of Ethics which provides:

10. To offer on all sales and trades, a 10-day return privilege on any item purchased or traded, unless I have clearly and conspicuously stated that items are sold or traded "as is," and without a return privilege.

Thus if there is disagreement about the condition of a chip, I know that I can quickly resolve it with another club member.

Of course if the chipis in a slab, I can't get a really good look at it and I just have to take the slabbers word for it.