Postage Stamp Catalog Guide: Understanding Scott, SG & Michel Numbers

Stamp catalogs are the backbone of philately. They assign unique identifying numbers to every stamp issue, list varieties, provide pricing guidance and establish the shared vocabulary that collectors and dealers use worldwide. However, the existence of multiple catalog systems can be confusing for newcomers. This guide explains how the major catalogs work, how to read their listings, and how to cross-reference between them.

The Major Catalog Systems

Four catalog publishers dominate the philatelic world. Each has a geographic strength and a slightly different numbering philosophy:

Other notable catalogs include Unitrade for Canada, Sassone for Italy, Edifil for Spain, JSCA (formerly JSDA) for Japan, and Zumstein for Switzerland. Each of these uses its own numbering system, adding yet another layer of potential confusion when trading internationally.

How Catalog Numbers Work

Each catalog assigns numbers chronologically within a country's stamp issues. The first stamp issued by a country is typically number 1. Subsequent issues follow in order of release. When varieties of the same design exist (different perforations, watermarks, or colours), they receive letter suffixes or sub-numbers.

For example, the world's first postage stamp — the Penny Black of Great Britain, issued 1 May 1840 — is:

• Scott #1
• SG #1 (one of the rare cases where the numbers agree)
• Michel #1
• Yvert #1

However, agreement quickly diverges. By the time you reach Victorian-era issues from the 1880s, Scott and SG numbers can differ by dozens. For 20th-century stamps the gap can be in the hundreds, because each catalog makes different decisions about what constitutes a new issue versus a variety.

Reading a Catalog Listing

A typical catalog listing contains the following information, though the format varies by publisher:

• Catalog number — the unique identifier for this stamp type.
• Illustration reference — a number pointing to a design illustration elsewhere on the page or in an appendix.
• Denomination — the face value printed on the stamp.
• Colour description — e.g., "deep blue," "carmine-rose," "olive-green." Colour is a major variety determinant.
• Date of issue — sometimes exact, sometimes just the year.
• Perforation gauge — given as the number of perforation holes per 2 centimetres (e.g., "perf 14" or "perf 12½ x 13").
• Watermark — referenced by a watermark number defined elsewhere in the catalog.
• Printing method — engraved, lithographed, typographed, photogravure, etc.
• Values — prices for mint and used conditions, sometimes with separate prices for never-hinged mint.

Condition Abbreviations

Stamp condition is described using standardised abbreviations that appear throughout catalog listings, dealer descriptions and auction lots:

Catalog Values vs. Market Values

One of the most common misconceptions among new collectors is that catalog value equals selling price. In reality, catalog values are retail reference prices that serve as a relative measure of scarcity. Actual market prices are influenced by:

• Supply and demand — popular countries and topics command prices closer to or above catalog. Less collected areas may sell at 10–30% of catalog.
• Condition — as noted above, catalog values assume VF. A poorly centred or faulty stamp sells well below catalog.
• Selling venue — auction results, dealer retail, online marketplaces and private sales all yield different price levels.
• Market trends — collecting tastes shift over time. Chinese stamps have surged in value over the past two decades; some European areas have softened.
• Minimum values — catalogs assign a minimum value (typically $0.25 in Scott) to even the most common stamps. Bulk common stamps sell for far less per unit.

How to Look Up a Stamp

If you have a stamp and need to find its catalog number, follow this process:

1. Identify the country — look for country names, inscriptions, or currency denominations. Use the inscription tables in the front of the Scott catalog for unfamiliar scripts.
2. Determine the approximate era — printing technology, design style and denomination can narrow the period.
3. Turn to the relevant section — catalogs are organised alphabetically by country, then chronologically within each country.
4. Match the illustration — find the matching design among the catalog illustrations.
5. Verify the details — check denomination, colour, perforation and watermark to confirm the exact catalog number.

Online tools can accelerate this process. StampID's AI identification can match a photo to the correct stamp and provide the Scott, SG, or Michel number instantly.

Online Catalog Resources

Several online databases complement printed catalogs:

• Colnect — a comprehensive, free-to-browse worldwide catalog with images and multiple catalog cross-references.
• StampWorld — free access to a large database of worldwide stamps with their own numbering plus cross-references.
• Stanley Gibbons online — searchable digital access to SG listings (subscription required for full details).
• Michel online — digital edition of Michel catalogs available by subscription.
• Zillions of Stamps — market-price database based on actual eBay sales, useful for gauging true market value versus catalog.

Cross-Referencing Between Catalogs

Because the same stamp has different numbers in each catalog, cross-referencing is a constant necessity when trading internationally. An American collector listing a stamp with its Scott number will confuse a European buyer who uses Michel. Strategies for cross-referencing:

• Use Colnect or StampWorld, which list multiple catalog numbers for each stamp.
• Include a scan or photo alongside the catalog number to avoid ambiguity.
• When selling internationally, list at least the Scott and SG numbers, as these are the two most widely recognised systems in the English-speaking world.
• Note that some catalogs split issues differently. One catalog may list a set as a single number with sub-varieties, while another assigns separate numbers to each value in the set.

Why the Same Stamp Has Different Numbers

The divergence stems from each publisher's independent editorial decisions. Key reasons include:

• Different start dates — Scott and SG both began cataloging in the 19th century but made different choices about which issues to include.
• Variety recognition — one catalog may recognise a shade variety as a separate listing while another groups it with the base stamp.
• Chronological disputes — if two stamps were issued close together, catalogs may disagree on which came first.
• Political decisions — some catalogs exclude stamps from entities they do not recognise as legitimate postal authorities.
• Back-of-book listings — airmail, postage due, official and revenue stamps are numbered in separate sequences, and each catalog draws the boundaries differently.