What is the difference between imperforate and perforated stamps? Take a look at the four stamps found on the page header. There are three imperforate stamps (from left to right - first stamp, third stamp and fourth stamp) the second stamp is the only perforated one.

Perforated stamps have the little holes between the stamps to easily separate them. Imperforate stamps do not have the holes. When the first stamps were printed (1840) postal workers would take a pair of scissors and cut the stamps apart. Large businesses and mail users would have workers use a razor to cut rows of stamps, several sheets deep, to speed up the process of separating the stamps. This was quick but many of the imperforate stamps ended up with uneven margins and sometimes portions of the stamp were missing. Early imperforate stamps are commonly found with the design cut into, uneven margins or having small portions of another stamp visible.  It was not until 1847 that a machine was invented to perforate stamps. The first machines used a process where small blades would cut into the stamp margins, this is called rouletting. The stamp sheets could be folded and torn apart but there was a problem with the blades cutting into the bed placed beneath the sheet of stamps and the blades themselves required constant sharpening and replacing. Additional modifications were made to early perforating machines and designs and by 1857 nearly all stamps issued throughout the world were perforated. Periodically, imperforate stamps have been issued by countries due to shortages of materials, internal political conflicts, as a consequence of an ongoing war, by accident or error and even by design.