The penny black is the first stamp ever issued and the first to use gum on the back they were issued in 1840 in the UK ,this one is mint and 1840 1d Black (OH) plate 5, imperf 3 margins, tiny thin upper right. SG 2. Cat £12,500.Now if your like me (What does that Gobley geek mean)Here is the Reply from the Stamp Dealer I bought it off.

The Penny Black is the most famous stamp because it was the first stamp issued. The Plate number refers to the copper plate that was used to print the stamp. Imperf means it has no perforations such as we have today to separate stamps. They used to use scissors and cut them. 3 Margins refers to the space around the stamp. So, if they cut into it there would not be a margin of generally the white space that was between stamps. The last auction house to have this stamp through was Mowbrays Auctions in Otaki near Wellington. They are along with auckland city stamps one of the two main auction houses in NZ . a thin refers to an area where some of the area of the surface of the stamp has worn away. Sometimes also you will hear adhesion, which refers to when perhaps some of the album page has become stuck on the stamp. Or tear. That is where there is a small tear etc