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.
Original images taken with a decent Sony camera
Zooming in just a bit already highlights the imperfections of the overprint. It appears the overprint was added some time after the stamp was cancelled. It’s also possible that the cancel was chemically reduced. The font appears ‘blobby’ and most of the letters don’t have nice straight lines. On the other hand the 6ds font looks much better although a bit faded.
RGBW
This is the best the best comparison I was able to obtain from all the filters I played with. It clearly shows imperfections on the overprint which to me indicate it was not applied evenly. The 6d does not show any such signs.
YUV_U
This filter makes the fake overprint look a bit better than it really is.
YUV_U inverted
LCHLUV_L
These last 2 filters just iterate the points I made about. The 6d looks particularly crisp when using the LCHLuv filter.