Identification
How to Read a Stanley Gibbons (SG) Number
A Stanley Gibbons, or SG, number is the reference number the Stanley Gibbons catalogue gives each stamp, used to identify it precisely. Numbers run in sequence through each country's issues in order of release, and a letter suffix marks a variety, such as a different shade, perforation or watermark. Quoting an SG number tells any collector or dealer exactly which stamp you mean.
At a glance
What an SG number is for
The purpose of an SG number is precision. Two stamps can look almost identical yet differ in shade, perforation or watermark, and so be different stamps with different values.
The SG number removes all doubt: it points to one exact stamp in the catalogue. When you see a stamp described as "SG 43" or similar, that number is its identity. Our guide to Stanley Gibbons catalogue value explains how the same catalogue also prices each stamp.
How the numbering works
- Sequence. Numbers run in order through each country's stamps, broadly by date of issue, so lower numbers are generally earlier.
- By country. Each country has its own sequence, so an SG number is always read together with the country.
- Suffix letters. A letter after the number, such as "a" or "b", marks a recognised variety of the same basic stamp, for example a different shade, perforation or watermark.
- Specialised numbers. Stanley Gibbons also publishes specialised catalogues with more detailed numbering for collectors who study a country in depth.
What a catalogue entry contains
- SG number
- The unique reference that identifies the stamp.
- Suffix letter
- Marks a recognised variety, such as a shade or perforation.
- Description
- The issue, denomination, colour and key detail.
- Value
- A guide price, usually shown for mint and used.
How to find a stamp's SG number
Identify the stamp.
Establish its country, denomination, design and issue.
Check the technical details.
Note the watermark and perforation, which distinguish similar stamps.
Match it to the catalogue.
Find the matching entry in the Stanley Gibbons catalogue, which gives both the SG number and the catalogue value.
SG numbers and value
Number and value are not the same
An SG number and a catalogue value go together, but they are not the same thing. The number identifies the stamp; the catalogue value is a guide price for it in a stated condition, and is usually higher than the price a stamp actually sells for. Our guides to Stanley Gibbons catalogue value and catalogue value versus market value explain the difference.
Frequently asked questions
It is the reference number the Stanley Gibbons catalogue assigns to each stamp, used to identify it precisely. Numbers run in sequence by country, with letter suffixes for varieties.
A letter suffix marks a recognised variety of the basic stamp, such as a different shade, perforation or watermark.
Identify the stamp by country, denomination, design, watermark and perforation, then match it to the Stanley Gibbons catalogue, which gives the number and the catalogue value.
No. The number identifies the stamp; the catalogue value is a separate guide price, usually higher than the actual selling price.
Founder and stamp dealerLast updated June 2026