The procedure I use is to send a board immediately when they call in the problem, bill them for it and credit the same amount when the defective board is received by me.
As I said the "match to DS2411" will work, send your customers a replacement board once and you can send chips afterwards.

Thanks for sharing that procedure.

If your "clues" are correct, how are you going to hadle it when someone not knowing what goes on send you an illegal board?

Not yet thought of what to do in that event what do you suggest?

One little bit of advice. I have, in my routine that the DS2411 is read till two consequtive reads give the same result, I do not know if that is needed, but I do so "just to make sure".

Whats the probability that the two consequtive reads read diffrent serial?

Thanks & Regards,
Prahlad Purohit