I think it is not authentic 1samuel 17 chap describes about the fight david fought with goliath, 1samuel 17.48 explains that david put a stone and slang it to goliath in his forehead and the stone penetrated in his skull thus in the image shown goliaths skull with the stone is not accepted as the stone was buried inside the skull it was nt attached to the skull.

And about goliaths skeleton found, 1 Samuel chap17 verse 51, 54 describes david cut off goliaths head and took it to Jerusalem, in the skeleton found skull is attached to the body in his grave, how is it possible if david cut goliaths head and today goliaths body is found with head.