perforations and watermarks - some tips

Disclaimer – these observations are made with the sole intention of assisting collectors. Apex Philatelics Ltd accepts no responsibility for loss or damage, however caused, as a result. If this condition is unacceptable to you, then please disregard these observations.



Perforations are the holes at the edges of stamps, punctured in the paper so that stamps may be torn from the sheets, rather than cut with scissors.

The philatelic standard for perforations is the number of holes per 2.00cm (20mm). The smaller the holes, the more there are in each 20mm.

If there are 10 holes per 20mm, this is "perf 10"

If there are 15 holes per 20mm, this is "perf 15"

and so on

However, where there is not an exact number of holes per 20mm

then the measure is given to the nearest ¼ (sometimes to the nearest ½). Best way to measure when you do not have any instrumentation is to count an exact number of holes, measure the length and then pro rata – for example

25 holes per 40mm = 12 ½ holes per 20mm = perf 12 ½

35 holes per 40mm = 17 ½ holes per 20mm = perf 17 ½

where the number is not exact, the figure (gauge) is given to the nearest ¼ - for example

23 holes per 38mm = 12.19 holes per 20mm = perf 12 ¼

23 holes per 37mm = 12.43 holes per 20mm = perf 12 ½

22 holes per 38mm = 11.57 holes per 20mm = perf 11 ½

22 holes per 37mm = 11.89 holes per 20mm = perf 12

21 holes per 38mm = 11.05 holes per 20mm = perf 11

21 holes per 37mm = 11.35 holes per 20mm = perf 11 ¼

(but note that

84 holes per 147mm = 11.42 holes per 20mm = perf 11 ½

apparent difference 0.25 – actual difference 0.07)

Stamps which are, for example, of a gauge 14 on all four sides are called "perf 14"

Where the gauge differs top/bottom to left/right, eg 15 at top/bottom and 14 at left/right, then they are called "perf 15x14" (the first figure always referring to the top/bottom, the second always to the left/right).

A "compound" perf (eg "perf comp 11, 12") will usually have three sides perf 11 and one perf 12 (whilst "comp 12, 11" will usually have three sides perf 12 and one side perf 11). "Comp 11, 12, 13" usually means that two sides are perf 11 and the other two perf 12 & perf 13 respectively). (NB we say "usually" because there is no international standard we are aware of.)

"Perf 12 –13" is the result of an irregularly spaced perforator, so that the measurement taken through a randomly selected 20mm could be anywhere between gauge 12 & gauge 13.

The main different types of perforation are:

IMPERFORATE – where there are no perforations (stamps are separated from sheets using scissors)

ROULETTE – a series of lines, such as you might find on modern tear-off coupons

LINE perfs – where a sheet is perforated using a single line (or single lines) of perfs in one direction (for example horizontally) and is then reperforated in the other direction (in this example vertically) in the same manner. (Note - the most obvious distinguishing feature of stamps perforated in this manner, is that the holes in the corners of the stamps do not always line up perfectly, so that the corners may appear to be damaged. Whilst such an affect can be unsightly, it is a natural consequence and stamps displaying such characteristics are not damaged).

COMB perfs – where three sides of the stamp are peforated at the same time (eg top and two sides). The bottom of row 1 and the top of row 2 being the same, the fourth side is perforated when the three sides of the second row are processed. (The holes at the corners line up).

ROTARY perfs – perforated using a continuous (round) perforator, which can be line or comb (see above) in appearance.

ELLIPTICAL perfs – holes which are elliptical (not circular) in appearance. Modern GB stamps have a mixture of round and elliptical holes as a security measure (against fraud).

Measuring perfs

Given that the difference in value between a stamp perf 11 and one perf 11 ½ can be substantial, it is vital to get the measurement right.

The best type of gauge is one with clear plastic with a series of converging lines printed into it. The converging lines give an infinite number of combinations which will match any stamp and perfs can be measured with stamps still on an album page, or still on cover, or one stamp in the middle of a sheet (without separating that stamp from the rest). One of the best known is Stanley Gibbons "Instanta" (there are others).

The cost is unlikely to be as much as £10/$20

You can also buy electronic gauges. They do their job perfectly well, but are considerably more expensive (around ten times the price) than the plastic type. (Their main drawback is that they give the gauge to the nearest ¼ (and some to the nearest ½ only). The stamps in our example above perforated 11 or 11 ½ could in fact be perforated 11.12 and 11.38. An electronic machine (shouldn't, but) may give them both as 11 ¼ - the plastic type, being infinitely calibrated, shows the difference quite clearly.)

To save time when sorting, measure one stamp as a control, and then place subsequent examples on top, lining up the perfs at the left and running your eye across the stamp. If the perfs line up wholly all the way along, then they are the same guage (and if they don't then they are different). The physical difference between one whole gauge and another (eg perf 13 and perf 14) is usually obvious to the naked eye (the holes for perf 13 are bigger). In rectangular stamps, use the longer edge if possible.

The great advantage of the one-on-top-of-the-other method is that it will show up reliably even the smallest differences. It is therefore both faster and more dependable.

Philatelic effects ...

… are confined mostly to cash values.

Imperforate stamps should have margins all the way round the design (rectangular stamps will be described as "4 margin"). Stamps with less than 4 margins (or less than 3 margins for triangular stamps) are worth considerably less than full-margined examples. (Note - stamps which are imperforate as a result of a printing error (ie which would normally be perforated) are best collected in pairs, or (very much a 2nd best option) as marginal singles. [This is to show a completely imperforate edge wide enough such that the stamp cannot be confused with a perforated stamp, which has simply had the perforations cut off])

Perforated stamps should have full and preferably even perforations all round. Missing or visibly shortened perfs devalue the stamp. (Notes – a) every stamp has one perf shorter than the rest. It is only where the perf is not "full" by a reasonable definition, that the stamp is devalued. If you feel the need to use a micrometer to measure the lengths of perfs, it is your choice, but we respectfully suggest you are going too far! – b) catalogues may mention which perforating process has been used, though often only where the same stamp has been manufactured using more than one process. The GB PUC £1 stamp of 1929 was perforated using the line process and 9 copies out of 10 have at least one corner with the distinctive out-of-synch characteristics. Such copies are NOT damaged and not financially devalued; their inclusion in a collection is a matter of simple aesthetic choice.)


Are put into the paper during the papermaking process. They are intended as security measures against fraud. Early stamps were generally printed on watermarked paper; in more recent years, more and more stamps have been printed on un-watermarked paper.

A common English philatelic abbreviation for watermark is ‘wmk.' (French or Spanish 'fil' (for filigrane/filigrana, German 'Wz' for Wasserzeichen)

There have been countless dozens, indeed hundreds of different watermarks used worldwide since the first stamps in the mid 1800s. Illustrations of the watermarks used are to be found in most catalogues, except the simplified ones, from all publishers. (The illustrations in an out-of-date catalogue are the same as the ones in current editions. Out of date catalogues can usually be purchased for a small fraction of the ‘new' price.)

Do remember that the illustrations in stamp catalogues are generally shown as if the stamp was viewed from the front - through the design – whereas watermark detection is usually done looking through the back of the stamp. Watermarks viewed from the back will appear to be reversed (as in a mirror image – see also below) when compared to catalogue illustrations.

(Most) Stanley Gibbons' catalogues have excellent sections, with illustrations, in the pre-amble to their listings, as do the other major cataogues, Michel, Scott, Yvert etc. SG, helpfully, usually illustrate watermarks actual (full) size, whilst other catalogues often use reduced-size illustrations.

The ‘normal' way for a watermark to appear on a stamp is ‘upright.' That is to say that the design of the stamp and the watermark are in the same top-to-bottom plane; if the watermark is at the top of the stamp, then the top of the watermark would be at, or point to, the top edge of the stamp. (Often noted as ‘upr wmk.')

In the opposite case, where the watermark was at the top of the stamp, but the bottom of the watermark was at, or pointed to, the top edge of the stamp, the watermark would be said to be ‘inverted'. (Often noted as ‘inv wmk'.)

Where the design of the stamp and the watermark are at right angles to each other, the watermark is said to be ‘sideways.' (Often noted as ‘side wmk')

Where the watermark appears from the back of the stamp in the same way as in the catalogue illustration, then the watermark is ‘reversed.' (Often noted as ‘rev wmk.')

There are other positions/types of watermark such as ‘diagonal' or ‘spiral' whose meanings should be self-explanatory.

Sideways watermarks can point either to the left and the right. In the case of many GB Wilding issues (of the 1950s and 1960s) stamps with sideways watermarks are frequently found pointing in both directions. This is normal; they were issued that way.

In cases where the normal issue has a sideways watermark and the normal issue did not have both left and right pointing variations, then any stamps having a watermark pointing in the unusual direction (eg normally to the left, unusual would be pointing to the right, would be said to be ‘watermark sideways inverted' (Often noted as ‘wmk side inv.')

Any combination of watermark is theoretically possible eg ‘sideways, inverted and reversed.' Abnormally facing or positioned watermarks are often worth a premium, sometimes a substantial premium, though this is not always the case. (The GB 6d embossed of 1847, for example, was "normally" issued with an upright watermark. In practise, it is extremely hard to find with an upright watermark; most examples have the watermark inverted.)


(Much easier in theory than in practise …)

Place the stamp against a black background or hold up to the light. If the watermark is not obvious, keep trying.

There are machines on the market, which assist to a greater or lesser degree, but we have not found any of them do much more than to show up more clearly watermarks we could already see, and be of far less help for others. We should also say that several of our customers have given good reports of the Signascope. (about £150 – try to borrow one and make up your own mind before buying).

(Tips ... ...

i) the so-called ‘Script CA' watermark common on Commonwealth GV stamps (replacing the ‘Block CA' around 1912/15) is far harder to see than the Block CA. The paper used was apparently slightly thicker, often with an additional chalky coating, and the watermark made fainter. The Block CA is usually easy to see, so that in general if you can't see the watermark (on these issues) it is an odds-on bet that it is the Script variety.

ii) compare also colours/papers - stamps re-issued with a different watermark were reprinted. The paper used may have been similar to the first issue, but it will not be identical. Likewise, the colours will not be an exact match.

iii) perforations - (GB) sideways and inverted wmks usually came from booklets or coils, where the perforations were guillotined (smooth edge under magnification) rather than torn (rough edge). A re-issue with a diferent wmk my have a line perf (irregular corners - see above), rather than comb perf.

iv) balance of probability - the chances are you don't have the rare variety. Double the catalogue value usually implies rather more than double the scarcity.

However ... ... I'm afraid that in the field of watermark detection, there are few shortcuts and no substitute for practise, practise and more practise.



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