How to identify and catalogue postage stamps
Watermarks, perforation gauges, and design details — the systematic approach philatelists use to pin down an exact stamp variety.
Reading the design and inscription
The most immediate identification clues are the country name, denomination, and design subject. Most stamps printed after 1880 carry the country name explicitly, though some countries use their native-script name or a recognised abbreviation — 'HELVETIA' for Switzerland, 'MAGYARORSZÁG' for Hungary, 'NIPPON' for Japan. For earlier stamps, and for some periods where country name was omitted (as was common for British issues before the Universal Postal Union required it), the design, vignette subject, and typography narrow the field considerably. After establishing country and approximate era, the denominator written on the stamp and the printing method — typographed (flat colours), engraved (raised ink texture), or photogravure (screened photo-like detail) — further guide identification. PhilLens recognises these elements automatically, but building visual familiarity with the major national stamp families sharpens your eye for unusual or unlisted varieties.
Measuring perforations and why gauge matters
Perforations — the rows of holes punched between stamps for easy separation — are measured by how many teeth (or holes) appear in a 20mm span. A perforation gauge tool (or a digital gauge in PhilLens) counts the teeth to give a reading like 'perf 12' or 'perf 11½'. The same stamp design was often printed with different perforation gauges in different printings, and the rarer gauge combination can be dramatically more valuable. The classic example is the US 2-cent red Washington stamp of 1890: perforated 12 is a common stamp worth a few dollars in used condition, while the perforated 8½ variety is a major rarity worth thousands. Beyond gauge, check that all perforations are intact, evenly spaced, and of consistent length — short perfs, pulled perfs, or a single missing perf all reduce value. When selling a stamp that might be a scarce perf variety, having it expertised confirms the gauge measurement and provides documentation that supports the premium price.
Detecting watermarks and paper varieties
Watermarks are patterns formed in the paper during manufacture, visible when held to backlight or placed in a watermark fluid. Major British Commonwealth stamps distinguish multiple watermark varieties that define distinct catalogue entries — the difference between a Crown CA and a Multiple Crown CA watermark on a colonial stamp can be a hundredfold difference in value. US classic stamps distinguish single-line and double-line watermarks and watermarked versus unwatermarked paper. To detect watermarks, place the stamp face-down in a black watermark tray and add a few drops of benzine or a proprietary watermark fluid (both evaporate without damage to the stamp); the watermark pattern becomes visible through the translucent paper. Alternatively, holding the stamp horizontally under a strong raking light sometimes reveals the watermark without fluid. For stamps where the watermark is critical to identification, documenting it with a photo is valuable for your collection records.
FAQ
How do I measure a perforation gauge accurately?
A physical perforation gauge is a card or plastic tool with printed rows of dots at various gauges; you align the stamp's perf tips with each row until you find the exact match. PhilLens includes a digital gauge tool that analyses the stamp image to count perforations automatically. For compound perfs — where the horizontal and vertical perf gauge differ — measure each side independently and express the result as 'perf 11 x 10½' (horizontal x vertical).
Are first-day covers valuable?
First-day covers (FDCs) — envelopes bearing stamps cancelled on their first day of issue with an official first-day cancellation — are a distinct collecting area with their own valuation logic. Most modern FDCs produced since the 1960s have limited philatelic value because millions were made to meet collector demand; exceptions include cacheted covers from noted cachet makers and those with rare stamp varieties or machine cancels from specific post offices. Older FDCs from the first half of the 20th century, especially those with hand-addressed envelopes to known collectors or bearing multiple stamps from a set, can be genuinely collectible. Condition for FDCs includes the envelope's freshness, the clarity of the cancellation, and the quality of any cachet design.
What is expertising and when do I need it?
Expertising is the process of having a recognised philatelic expert or foundation examine a stamp and issue a signed opinion or certificate attesting to its genuineness, identification, and condition. For high-value stamps — typically items worth $200 or more — a certificate from a recognised expertising body (the Philatelic Foundation in the US, the British Philatelic Association expertising service in the UK) provides the documentation that serious buyers expect and that justifies a premium price. Without expertising, sellers of rare stamps face buyer scepticism and may need to discount significantly. PhilLens helps with initial identification to tell you whether an item is worth pursuing expertising.