where?
on the spinner or on the checkerboard or on the olive drab anti glare panel? not sure what you are referencing.
if your talking about the spinner: that small little black dot on the tip of the spinner should be there (it is hard coded on) it represents the small indentation on the tip of the spinner I think hehe.
if your talking about the checkerboard pattern: my references show it is checkerboard on top of the nose too.
if you arte talking about the black crew plaque with white lettering on the left side of the antiglare panel: my black and white world war II photograph I used as reference shows this plaque on the actual plane. also the duxford P-51D repainted to match this scheme has the plaque.
if this is the controversy area it sounds like it could have been added at a later date than some photos but it is completely authentic to the origional scheme right down to the crew names on the plaque.