The BlogIdentification
Stamp Perforations and Watermarks Explained: How Collectors Identify Look-Alike Stamps
Two stamps can look identical and still be very different issues. Perforation gauges and watermarks are how collectors tell them apart.
Have you ever found two stamps with the same design, color, and value, and wondered if they are the same? Often they are not. Small details like perforations and watermarks can separate a common stamp from a more desirable variety. Learning to check them is one of the most useful skills a collector can build.
What Are Perforations?
Perforations are the rows of small holes punched between stamps so they can be torn apart. The little points left on the edge of the stamp are called "teeth." Early stamps had no perforations and had to be cut apart with scissors. In the United States, perforated stamps arrived in 1857.
Why Perforation Measurements Matter
Printers used different perforating machines over the years. The same stamp design may exist in more than one perforation size, and catalogs list them as separate varieties. Sometimes one is common and the other is scarce.
How to Measure Perforations
Collectors measure perforations with a perforation gauge. The measurement is the number of holes (or teeth) within 2 centimeters.
- Place the stamp on the gauge.
- Slide it until the teeth line up perfectly with the dots or lines on one row of the gauge.
- Read the number beside that row, such as "Perf 11" or "Perf 12."
- Measure both the top and the sides. Some stamps have different perforations on each, written as "Perf 11 x 10½."
What Are Watermarks?
A watermark is a design pressed into the paper when it was made. It is thinner than the surrounding paper and usually cannot be seen from the front. Governments used watermarks to help prevent counterfeiting. Some U.S. stamps from the late 1890s through the 1910s were printed on watermarked paper, which is why watermarks are important for identifying many issues from that era.
How to Find a Watermark
- Hold it to the light. Sometimes you can see the watermark by holding the stamp up to a lamp.
- Use a watermark tray. Place the stamp face-down in a black tray. The watermark may appear as darker lines.
- Use watermark fluid. A few drops of fluid made for stamps can make the pattern visible for a moment, then evaporate without harming most stamps. Always follow the product's instructions and avoid using fluid on stamps with printing that may run.
Putting It All Together
When identifying a stamp, compare the design, color, perforations, and watermark with your catalog. Each detail narrows down the exact issue. Condition still matters, too. For more on what drives value, read How to Tell If Your Old Stamps Are Worth Anything.
Need a Second Opinion?
If you have stamps that look alike and you are not sure which variety you have, Carolina Mountain Stamps is glad to help. Reach out or browse our collections to see examples.
