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A stamp’s perforations can help distinguish printings that share the same general design. Different issues may have different horizontal and vertical gauges, and catalogs sometimes identify varieties by measurements such as 11, 11½ or 12. You should never rely on the perforation number alone to identify an issue.
What does a perforation gauge measure?
Perforation gauge refers to the approximate number of holes or teeth in a length of 20 millimeters. The measurement is a convention, not a count of every hole around the stamp. The gauge may differ on opposite orientations or edges, so inspect the relevant sides carefully.
Using a traditional perforation gauge
Place the stamp on a clean, flat surface and handle it with smooth philatelic tongs. Position the perforation edge along the gauge’s printed dots or lines. Find the spacing that aligns consistently with the holes across a sufficiently long portion of the edge. Repeat for the opposite edge and the other orientation if needed. Avoid forcing delicate edges into a measuring slot.
Interpreting compound perforations
A stamp described as perforated 11 × 12 typically has a different gauge horizontally and vertically; catalogs generally state the horizontal measurement first. Check the convention used by your reference, especially when comparing older specialized literature. Record both dimensions, not simply the first number you observe.
Sources of measuring error
Short edges can be hard to align. Bent or missing teeth, worn gauges, poorly reproduced scales, separated booklet edges and trimmed material can distort the apparent result. A clearly damaged edge may be impossible to measure reliably. Compare against a known reference example when practical.
When to consider an electronic gauge
An electronic device may be useful for collectors who repeatedly examine specialist perforation varieties. Confirm the stated measuring range, calibration method and manufacturer documentation. Electronic output still requires interpretation and does not authenticate a stamp by itself. Read our SAFE Perfotronic 2 guide.
Perforation identification in context
Examine watermark, color, paper, printing method, design details and issue date as relevant. A specialized catalog or expert reference can help determine whether the measured difference corresponds to a recognized variety or routine measurement uncertainty.
Frequently asked questions
Can I use a ruler? A specialist printed gauge is usually easier for consistent matching, although the underlying convention is based on 20 millimeters. Is an electronic gauge more accurate? Not necessarily in every case; proper calibration and damaged edges affect results. Can the perforation gauge prove a stamp is rare? No. Multiple attributes and reliable catalog evidence are needed.
Choosing equipment
A simple manual perforation gauge is usually an excellent starting point. Dedicated electronic tools are optional specialist equipment. Explore the existing equipment directory.