michiganjfrog , there is no way of telling if a player has been hacked or not just by looking. And no way would a seller reply you and tell you that their players are hacked.
Usually these nano-clones are of the 2.5mm jacks, but you could buy a 2.5mm to 3.5mm converter plug.
i'll suggest that if you would like to buy a nano-type player, try
uxcell.com instead, as their products are usually what they are advertised to be.
Or
HouseOfDAP.com, where they sell slightly higher end players with much better functions (like the T29 and Meizu).