Parker Duofold Black Barrel Discoloration

[Rob Saccone]

I purchased a vintage Parker Duofold Fountain Pen which is black today at a local pen show.  It works perfectly well.  However I noticed that since I’ve gotten it home and been handling it the black color of the barrel has been discoloring from when I purchased it earlier in the day.  It is visibly lighter than the cap and has a greenish hue to it.  The cap is still dark black.  It wasn’t discolored when I bought it and seems to have started discoloring with handling.  The part of the barrel covered by the cap when screwed on is still a deep black when I take off the cap.  Can someone tell me what is happening with it and if there is a way to bring the dark black color back?  

 

Thanks,

Rob