Standards · Philately
Stamp Centering & Soundness
Stamps are evaluated against three independent axes — centering (position of the design within the perforations), gum (state of the original adhesive) and soundness (absence of faults) — a framework established by the Royal Philatelic Society London and the Philatelic Foundation and adopted universally by modern certification bodies. Xene's centering tolerances are documented digitally to 0.1 mm and published in the Standards Manual; the gum and soundness assessments follow RPSL conventions with explicit disclosure of all faults on the certificate face.
Historical origin
Formal philatelic certification emerged in the mid-20th century as forgeries, reperforations and regummed examples proliferated on the auction market. The Philatelic Foundation (New York, established 1945) and the RPSL Expert Committee (London) developed the opinion letter as the primary authentication instrument. Numerical centering grades were later adopted from numismatic practice; the adjectival tiers in current use — Fine, Very Fine, Extremely Fine, Superb — were standardised by the American Philatelic Society and Scott Publishing in the 1980s and remain the accepted vocabulary for US and British Commonwealth material.
Centering scale
Centering is graded adjectivally across six tiers: Average, Fine (F), Fine to Very Fine (F-VF), Very Fine (VF), Extremely Fine (XF) and Superb. The tier is determined by the margin ratio on the limiting axis — the side with the least space between the design and the nearest perforation tip. All four margins are measured; the worst single margin defines the grade.
Tolerance bands
Average: the design touches or cuts into at least one perforation tip. Fine: the limiting margin ratio is between 20/80 and 30/70 — the design is clear of the perforations but the imbalance is clearly visible. Fine–Very Fine: 30/70 to 40/60; balanced on at least three sides. Very Fine: 40/60 to 45/55; the catalogue-value benchmark. Extremely Fine: 45/55 approaching 48/52; near-perfect centering with full margins on all sides. Superb: essentially 50/50 with wide, equal margins on all four sides — the rarest and most prized centering tier for any issue.
Gum categories
Original gum (OG) is classified in descending order: Mint Never Hinged (MNH) — gum fully intact, undisturbed, no trace of hinge adhesive; Mint Lightly Hinged (MLH) — a faint hinge impression visible on the gum only; Mint Hinged (MH) — hinge applied and removed, leaving a clear impression; Hinge Remnant (HR) — a paper hinge or portion thereof still adheres to the gum; No Gum (NG) — gum fully absent, whether issued thus or subsequently removed; Regummed (RG) — gum replaced after original loss, declared on the certificate and penalised accordingly.
Soundness
A sound stamp is free of thins (areas of reduced paper thickness), tears, creases, stains, soiling, repairs, reperforations, short perforations (measuring below gauge on one or more sides) and pulled perforations (perf tips removed). Faults are reported on the certificate by type, approximate location and severity. Their presence does not preclude certification, but a stamp with any fault is ineligible for the highest centering tiers and is valued at a substantial discount to a sound example of equal centering.
Perforation measurement
Perforations are measured with a calibrated gauge against the published specifications for the issue. Most major catalogues list perforations to the nearest half-gauge unit (e.g. 11½, 14). A stamp with perforations differing from the standard variety for the issue — by as little as half a gauge unit — may represent a separate listed variety with its own catalogue value, sometimes many times that of the standard perforation. Xene records the measured gauge on every certificate.
Common dispute points
The most frequent disputes concern the VF/XF boundary (where margin ratios of 44/56 may reasonably be graded either tier by different examiners); the disclosure threshold for minor soiling on the front face; and the treatment of natural paper inclusions versus foxing. Xene resolves VF/XF boundary cases by measurement rather than visual impression and notes the precise margin ratio on the certificate, allowing the collector to assess the assignment independently.
How Xene differs from other certification bodies
Xene issues a four-axis margin report — top, bottom, left, right as individual measurements — rather than the single worst-axis summary used by most opinion-letter services. This provides the market with complete information: a stamp with one tight margin and three generous ones is distinguishable from a stamp tight on two sides, even if both fall within the same adjectival tier. Xene also photographs both faces and the gum under raking light, with all images stored on the online registry and accessible via the certificate QR code.
Edge cases and 'Faulty' designations
Stamps with structural faults that prevent any centering grade from being assigned — including tears across the design, half-stamps, or stamps on piece with damage obscuring a complete measurement — receive a 'Faulty — Authenticated' designation. Stamps where the authenticity is in doubt receive an 'Inconclusive' opinion with a written commentary. Reperforated stamps are identified using a micro-gauge comparison of individual perf tip spacing and receive a 'Reperfed — Authentic' notation. No premium-registry listing is possible for faulty or reperfed examples.
Reference table
At a glance.
| Centering grade | Margin ratio (limiting axis) | Brief description |
|---|---|---|
| Average | Below 20/80 | Design touches or cuts into one or more perforation tips |
| Fine (F) | 20/80 – 30/70 | Design clear of perfs; one side markedly narrower than others |
| Fine–Very Fine (F-VF) | 30/70 – 40/60 | Balanced on at least three sides; one side noticeably narrower |
| Very Fine (VF) | 40/60 – 45/55 | Well balanced on all sides; catalogue-value benchmark |
| Extremely Fine (XF) | 45/55 – 48/52 | Near-perfect; all margins generous and approximately equal |
| Superb | Essentially 50/50 | Equal margins on all four sides; Jumbo dimensions typical |
Questions
- Why is Very Fine the catalogue-value benchmark?
- Most major catalogues — Stanley Gibbons, Scott, Michel, Yvert — price stamps at the Very Fine grade. Extremely Fine and Superb examples command multiples of catalogue value; Fine and below trade at a discount. Collectors comparing prices between catalogues should verify which centering tier each uses, as conventions differ slightly between British Commonwealth and US material.
- What is a 'Jumbo' stamp?
- A Jumbo stamp has margins significantly wider than the typical example for the issue, usually the result of a sheet being cut between stamps with more than average gutter paper. Jumbo margins can carry a Superb-centered stamp into a substantial premium category, particularly for classic 19th-century issues where centering below VF was the norm.
- Are perforations measured during grading?
- Yes. Perforations are measured against published issue specifications using a calibrated gauge. A stamp with perforations differing from the standard variety is a potentially separate catalogue listing and may be valued differently. Xene records the measured gauge on every certificate and cross-references the result against Scott, SG and Michel listings.
- Does a thin affect the centering grade?
- A thin does not directly affect the centering tier — centering is measured by margin ratios. However, a stamp with a thin is ineligible for the highest centering tiers at Xene, as the combination of a fault and premium centering would create a misleading market impression. Thinned stamps are capped at F-VF regardless of actual centering ratios.
- What is the difference between a short perf and a pulled perf?
- A short perforation is one that measures below gauge — i.e. the perf tip did not fully punch through the paper during production. This is a manufacturing defect and may be original to the printing. A pulled perf is a tip that has been physically torn away from an otherwise sound stamp. Pulled perfs are a fault; short perfs require case-by-case assessment as they may represent issued varieties.
- How does Xene handle stamps without gum?
- A stamp issued without gum (common for some tropical issues and some revenue stamps) is recorded as 'No Gum — As Issued' and is not penalised. A stamp that originally had gum but has had it removed is recorded as 'No Gum — Removed' and is valued accordingly. The distinction is made by examining the paper reverse under raking light and ultraviolet illumination.
- Can a stamp be re-certified?
- Yes. Any stamp previously certified by Xene or another recognised body may be submitted for re-examination. Xene makes no guarantee of replicating a previous opinion, whether its own or another body's. Re-examination uses the current-year rubric and measurement standards.
- What is the Xene PSE centering standard?
- PSE (Philatelic Stamp Exchange) centering standards — originally devised by the Philatelic Stamp Exchange in the US — use numeric ratios rather than adjectival tiers. Xene maps PSE numeric ratios to the adjectival scale used in this document. Where a PSE numeric ratio falls precisely on a tier boundary, Xene applies the lower tier conservatively.