Counterfeit 3850-NM-4-10G module?

[GrdLock1]

Bought a 3850-NM-4-10G from a seller with great feedback off Amazon a while back. Never used it. I sold it on eBay recently. The buyer is now requesting a refund claiming the part is counterfeit. 

Reasoning: "the plastic head sync fasteners are counterfeit units are are hexagonal while genuine are round. The back plate is hard stamped into the metal plate causing the the stamp to protrude from the back side. Fake ones will have a smooth bottom plate. See attached pictures."

I accepted the refund but now I'm worried I'll be stuck with this counterfeit part and it'll just be a complete waste of money. Are his reasons above legit? Does this mean the part I bought is counterfeit?

[balaji.bandi]

you get a much counterfeit product, that is the reason cisco always recommends to cisco partner or cisco refurbished partner.

cisco never take e-bay product and support. you can validate the authenticity with serial numbers.

[GrdLock1]

How do I validate it with the serial number though? I tried going to https://cway.cisco.com/sncheck/ and putting in the serial number and it shows a result but says

Product
Product ID
Unavailable
End of Sale
Not Announced
End of Support
Not Announced

Is it not possible this could still be legit and just be a slightly different revision of the hardware?

[balaji.bandi]

Should be some time it puzzled question - i am sure i have seen some cisco gear switches - before the cisco logo was exposed, the other one exactly same printed directly on the chassis white color. (it works as expected,as long as it working)

but your case looks different, but that is a fact, if cisco recognizes it will give you full details of new products.

[Leo Laohoo]

See those white stickers to the right?  Take a good picture of both of them and post it.  
I suspect they are different hardware "iteration".  

I do not believe they are "fakes" because the modules don't sell much.  It is the appliances that fakes abound.

[GrdLock1]

The pics were sent to be by the buyer of the module, so won't be able to grab a pic until I get it back, and the top one in the pic is another one he has, so won't be able to get a better pic of that one at all.