Imperforated stamps are postage stamps with
no perfins at any side, nor
rouletted. They are popular known as "imperfs".
The earliest
stamps were all imperforate. Likewise, many later self-adhesive stamps
are imperforate. Today most imperfs are part of a larger production
line, but with the normal perforation excluded. Not many modern stamps
are issued only as imperforated even as self-adhesive stamps are gaining
popularity
Some imperfs are referred to as errors, where the
perforation tools failed to perforate the paper sheet. Other imperfs can
be proofs where no perforation was required to examine the print.
