This is the 12 cent stamp from the 1851 issue.
Scott #17 is easy to identify. It only comes imperforate. When buying Scott #17, make sure youíre not buying a #36 with the perforations trimmed off. Any Scott #17 with extremely tight margins all around is suspect. Make sure your #17 has one or more larger margins that show no traces of perforation holes that were trimmed off.
Scott #36 and #36B are both perforated 15.5.
Scott #36 comes from Plate I. There are two ways to identify it. First, the color is like Scott #17, a gray-black color. To me, it almost looks like charcoal. The sure way to identify it requires a 10x or stronger magnifying glass. On #36, the outer frame lines are complete, but uneven from recutting. The frame lines were thin and one of the first parts of the stamp design to wear out. The lines had to be recut on the printing plate to make them complete.
Scott #36B is intense black in color. It comes from Plate III. If you put a #36B next to a #36, you can usually see the difference in colors. To verify #36B, check the outer frame lines. On #36B, the frame lines are broken, uneven, and sometimes only partially printed.
Like most of the 1851 issues, the stamp designs were placed very closely together on the printing plate. There was very little room for the perforation holes. The perforation holes normally come very close to the frame lines. If you find a copy where the perforations are well clear of the frame lines on all 4 sides, itís worth substantially more than the Scott catalog value.