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just for future reference, on all Macs since 2011, you have to take it to an authorized service rep
Oddly enough I am an authorized service rep!
They didn't tell me anything about this when they taught me the secret handshake! I also don't find anything about this at GSX the Apple Service Website!
Later: I "rephrased" the question I asked at the GSX website and did get the answer to this query. I know the answer is out there in the real world beyond GSX but I can't get to it by our content blocking here! Thanks Paddy!