The stamp comes from a roll of stamps, all stamps originally being perf'ed. in production on both sides, that was inserted into a stamp affixing machine used by businesses to automatically stamp envelopes for mass mailing. You can see by your example, the stamps in the roll were perf'ed. slightly off-center to begin with since the left hand perfs. are cutting into the design. The stamps, as dispensed by the affixing machine, cut the stamps from the roll as they affix it to an envelope. Sometimes, the stamps get out-of-alignment and when they cut the stamps, they sometimes cut them short of where the perforations are located on the individual stamp, especially where they were slightly mis-perf'ed to begin with. You see this quite a bit on W/F coiled stamps that have been used in affixing/dispensing machines.
