"But if B and C refuse to talk there is no reason to doubt A."

I agree for the most part, but some consideration needs to figured into the equation if there are multiple B's and C's. ...and in this case, collusion between the C's would be unlikely. ...possible, but unlikely.

...might be more along the lines of specialty collectors who would be both embarrassed by paying good money for a fake chip and admitting it.....

Collusion between the B's (after the original purchase of the fakes, and the exposure) is in my opinion the more probable scenerio. That, again in my opinion is where this mess began and currently sits.

I don't fault Jim in any way concerning his investigation.

There is much blame to be laid on the doorsteps of those responsible. Those are the people who need to own up to what happened. If they won't, it will continue to happen.

Bob