The Penny Black is not only the first stamp but one of the more fun stamps to specialize in. The stamp was printed in twelve plates, and each plate had 240 subjects. As a security measure, each stamp received check letters in the corners so that each of the 240 subjects of each plate are unique (the check letters made counterfeiting more difficult as forgers would have to reproduce more than one specific lettered stamp or the overabundance of the same check letter would lead to suspicion. Further, the check letters eliminated the concern that partially cancelled stamps would be soaked off, cut, and reassembled on letters). With twelve plates and 240 stamps per plate, a specialist has 2,880 different Penny Blacks that are needed to have a complete run of plates and check letters. Further, specialists can collect by cancellation and date, blocks, pairs, and multiples. Most collectors keep it simple and are happy to have one. We just bought a few Very Fine four margin, fault free Penny Blacks. These are tough to find as the margins between the stamps were small, and people who were using them on letters didn't think that collectors 170 years later were going to want four full margin stamps. Further, early collectors didn't care much for quality; so stamps were often torn or scraped off envelopes. But these three above are perfect, and they catalog $350 each.