Originally Posted by
cestmoi123
Problem is, if the passport is lost/stolen, and the number is associated with the person, not the document, then you've got (a) two passports out there with the same number, and (b) no obvious way to tell which one is the valid one.
The first pp has (say) 123456789; the replacement (if orig is lost) would be 123456789-1 (or 123456789A) [the issuance of a pp with a suffix, would invalidate all previous pps--passcontrol agents would know this when they scan a pp on entry/exit.]