Sometimes two stamps look alike and the only difference is the gauge of the perforations. Perforations are small rows of holes punched between stamps to make them easier to separate. We use a perforation gauge to measure the number of holes or teeth within two centimeters. If a stamp has 11 perforations in 2 cm, we say it’s “Perf 11.” Here are some tips on how to measure perforations:
- To measure your stamp, lay it on the center of your gauge.
- Slide the stamp up or down until the perforations on the stamp line up with the pattern on the gauge all the way down the length of the stamp. (If the perforations only line up with the gauge part of the way, then you haven’t found the correct gauge yet – keep trying!)
- Be sure to measure one horizontal side and one vertical side of the stamp, since many stamps have what is called “compound perforations.” They have a different perforation gauge on the horizontal and vertical sides. In catalogs, the horizontal perforation gauge is listed first, then the vertical. For example, the 1984 Winter Olympic stamps (US #2067- 70) measure perf 10 ½ x 11. That means there are 10 ½ perfs every 2 cm on the horizontal sides and 11 perfs every 2 cm on the vertical sides.