Thanks for Kudos!
If you have choice and can see few boxes of the same product, select higher serial number (this is my guess only).
Both my devices were / are with serial number WMC.
I have seen in shops WCC also, and I get for replacement used (re-certified) WCC series, which was probably older, and disk head was noisy.
This is my guess only.
One difference more:
My Book Live - 3 years warranty
My Cloud - 2 years warranty
But you do not want to use your right to warranty (mostly the only way is replacement) to replace device to one with uknown history (other manufacturers do the same).
Take care of it and prepare for possible recovery (there are ways on forum).
