When I purchased my D500 I thought I might just as well benefit from the recall of the EN-EL15 batteries - I had 5 and after contacting NIKON here in France, I sent the first three off to Paris. (Keeping two back to use...)
In less than two weeks I had received 3 brand new (2016) Li-ion20 batteries. So I sent off the remaining two.
I received them back today - however, much to my dismay, one of them hadn't been exchanged as it was considered counterfeit.
As far as I can tell everything was identical to the other batteries (except, obviously, the serial number) - I admit to having purchased this online (not from a shop) so I've been had. Beware!
So, moral of this story - even 'official' Nikon EN-EL15 are being counterfeited...what is the world coming too...
Cameras, lenses and stuff. (I actually met someone once who had touched a real Leica lens cloth.)
This is just one example. The one-stroke mistake on the EN-EL20 is even more subtle.
Hopefully you are getting an authentic battery in the box of course