How can i check if my new Nexus 6P was never used and is new

[AC Question]

I bought a international version of nexus 6p on ebay. Is there any way to tell if the phone is brand new, never used phone. I just want to make sure it is not refurbished or used by someone and reconditioned

 

[tony bag o donuts]

Multiple posts mention doing this:
Open the phone dialer app.
Type ##786# OR *#*#786#*#* ( No need to press Call button, it will automatically take you to the RTC screen)
But I have never tried it and don't know if it does any harm.