Lexmark CS410 Technical Reference Manual page 44

Data consists of an 18-digit identification code, which is composed of the following:
• A 2-digit post code
• A 2-digit billing district code
• A 6-digit customer account number
• An 8-digit item number
To enhance readability, "." characters (ASCII 46) may appear anywhere in the data; they are ignored. Three "."
characters are inserted automatically at the correct positions in the human-readable text printed with a Swiss
Postal bar code symbol, separating the four components of the identification code.
Invalid characters or lengths in the identification code are flagged with an error.
One-dimensional bar codes
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