Help me switch out this shower head

[dkurnik]

I am trying to remove and replace the showerhead in the picture. I don't know the brand. When I unscrewed the showerhead, I found the brass piece shown in the 2nd and 3rd pictures. That appears to be the socket part of the showerhead ball and socket joint. I tried to unscrew it, but it would not budge. It has been there for 32 years. Do you think it is screwed into a standard 1/2 NPT female thread behind the tile? Or do you think it is soldered into the plumbing behind the tile? How do you recommend I proceed? My goal is to install a standard shower arm and showerhead.