Catalogue Numbers
Catalogue numbers from various publishers appear in descriptions to aid identification. The general format is catalogue abbreviation followed by catalogue number (SC704, for example).
The numbering systems, including those listed below, remain the copyright of their respective owners.
| Numbering system | Country | Format |
| John Barefoot | Great Britain, Commonwealth | BFxxx |
| Jeffrey Booth | Great Britain FDCs | BCxxx |
| Brusden White | Australia | BWxxx |
| Connoisseur | Great Britain | CCxxx |
| Campbell Paterson | New Zealand | CPxxx |
| Collecting Slogan Postmarks | Great Britain | CSPxxx |
| Darnell | Canada | DLxxx |
| Deegam | Great Britain | DGxxx |
| Hibernian | Ireland | HBxxx |
| International Stamp & Coin | Brunei, Malaysia, Singapore | ISCxxx |
| Joseph Buttigieg | Malta | JBxxx |
| Michel | All | MIxxx |
| Murray Payne | Commonwealth | MPCCxxx |
| Pierron's | Great Britain, Commonwealth | XXXxxx |
| Ridgewood | Great Britain | RWxxx |
| SACC | Rhodesias, South Africa | SACCxxx |
| Scott | All | SCxxx |
| Stanley Gibbons | All | SGxxx |
| Stefan Heijz | Falkland Islands, BAT | SHxxx |
| Stoneham | Great Britain | STxxx |
| Urch Harris | Great Britain, Commonwealth | UHxxx |
| Yang's | Hong Kong | YGxxx |
| Yvert et Tellier | All | YTxxx |
| Zimbabwean Concise Catalogue | Zimbabwe | ZCxxx |