A while back I acquired the 1d Auckland Exhibition stamp which is part of the  1913 Auckland Exhibition issue. Immediately after seeing it I suspected that it was a fake as even on the photo the overprint looked odd.  Sure enough after putting a picture of the stamp through some filters the fake overprint shows up.  Here I’m going to provide a comparison with the 6d example, which I believe is legitimate.  I used retroreveal to scan the images.  Some fake may be worth more than the original, but I doubt this is the case here.  The 1d is out in abundance and I strongly suspect that there are more forgeries out there.  Hope there are some better ones than mine.