For some reason this variety of the 1888 8c yellow green stamp is not listed in the Stanley Gibbons catalogue even though most of the low values of this set have similar errors of perforation omission. Perhaps it is very uncommon.
You may say how would I know this is from the genuine stamp and not a Founier or Careme forgery? There are certain characteristics that indicate it is a genuine item.
In the genuine stamp, there is a coloured dot in the corner as shown and also the coloured background of the Postage & Revenue scroll does not touch the right outside frame line.
In addition there are two dots to the right of S which is usually obvious in later transfers and there is a faint large dot between N and T.
The forgery is actually very well executed. It is a lighter shade of yellow green. But there are a few features that can reliably differentiate it from the real thing. It can be a Carame or a Fournier forgery. It was thought that Carame passed on the printing plates to Fournier and some said that the Carame printings are better. I hope that someday we will have enough knowledge to distinguish between the two types reliably. Just came back from our SSS AGM weekend, I was informed by good authorities that it is possible to differentiate between the two by plating flaws. Plating is not my forte and to me it is a tedious means to an end. While this maybe be feasible with whole sheets, it is well nigh impossible with individual stamps.
There is no coloured dot in the corner here and also the coloured background of the scroll merges with that of the outside frame.
Here the the long rope from the mast is uneven in thickness. There are also other features including the bottom of N in North is wider at the bottom compared to the top. The left lower ornament is centered more to the left and the right lower centered more to the right. Both these two items have gum at the back. With Fournier/Careme forgeries, there is a thin layer of smooth gum whereas in the normal stamps, the gum is thicker and uneven with fissures and cracks. The genuine stamps are also printed on wove paper with distinct pattern of dots when viewed in front of light.