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Explanation: This means that not every material sub-group starts at number '1'. As an example, while coppers do commence at 001, miscellaneous copper alloys start at 100, copper aluminium alloys start at 300, copper zinc alloys at 500 and so on, as shown in table 1.
The lack of overlap in preferred number series ensures that common materials in differently lettered material groups will not normally share the same number. There will, however, be many spare numbers available in reserve.
Table 1: CEN European Numbering System for copper and copper alloys, showing the preferred number ranges and letters allocated to the different material groups.