Measuring Perforations, and Why It Settles Arguments

Perforation gauge is the number of holes in a 20 millimetre span, and it is one of the few stamp characters that is objective, quick to check and frequently decisive.

Why it exists as a measurement

Perforating machines were set up with pins at a particular spacing, and different machines and different printings used different spacings. A design reissued years later on a different machine gets a different gauge while looking identical.

Catalogues therefore list the same design several times, separated only by gauge, and the values can differ enormously.

How to measure

A perforation gauge is a card or plastic strip printed with rows of dots at known spacings, labelled 10, 10½, 11, 11½, 12 and so on.

Lay the stamp on the gauge and slide it up and down until the perforation holes align exactly with one row of dots across their whole length. That row's number is the gauge.

Measure both the horizontal and vertical edges. They are frequently different, and a stamp is described as "perf 11 x 10½" meaning horizontal then vertical.

Getting it right

Align across the full edge rather than a few holes. A close-but-not-exact fit over three holes will look convincing and be wrong, and half a gauge point is the difference that matters.

Measure the holes, not the paper between them. Damaged or reperforated edges mislead, and a stamp with an added row of fake perforations is a known forgery type.

Do not press hard. A gauge is a measuring tool and the stamp is the fragile object.

Coils and booklets

Stamps issued in coils are perforated on two opposite sides only, and booklet stamps frequently have one or two straight edges where they were cut from the pane.

A straight edge is therefore information rather than damage, and telling a genuine straight edge from a trimmed stamp is one of the more consequential judgements in the hobby. Genuine straight edges are clean and slightly rough at the cut; trimmed stamps usually show a suspiciously exact edge and reduced margins.

Reperforation

Adding perforations to a stamp that lacked them, or reperforating a damaged edge, is a common alteration precisely because gauge matters so much.

Signs: perforation teeth that are unusually uniform, holes that do not quite line up with the originals on the other edges, and margins that are narrower than the design normally has.

Anything valuable enough for the difference to matter is worth certifying, which is the argument forgeries, fakes and why certificates exist makes.

Where to start

Measure gauge as part of the routine identification sequence, alongside watermark and design. How to identify an unknown stamp sets out the order, and gauge is the step people skip most often because it seems too minor to matter.

Rouletting and other separations

Not every separation is a perforation. Rouletting cuts or pierces the paper without removing any, leaving a slit or a dashed line rather than holes.

Several varieties exist and are catalogued separately: roulettes in lines, in arcs, in serpentine curves. They are measured the same way as perforations, by counting cuts in 20 millimetres.

Die-cut self-adhesives are the modern equivalent, and their wavy die cuts are also gauged. A modern stamp with an unusual die-cut gauge can be a scarce variety in exactly the same way.

Buying a gauge

An inexpensive plastic or card gauge is adequate for almost everything. More precise metal gauges exist and matter for issues where quarter-gauge distinctions are catalogued, which is a small minority.

Start with the cheap one. If you reach a point where a quarter gauge is the question, you will know why you need the better tool.