Comparing how mine looks (The car's one and the two spare ones in my cabinet ) I can also say it's a genuine GX head. They don't have numbers only the NISSAN wording like yours.

These pictures, has it been taken recently when the head was removed? If so, those ports and combustion chambers look mightly clean for a used head. I am also planning to get mine done a bit with polishing and cleanup of casting imperfections.Hope it looks the same even after use.