Earliest reported postmark

The term Earliest Reported Postmark or ERP is a term used by the United Postal Stationery Society (UPSS) for the past 40 years. They have established a database in which the earliest postmarks on stamped envelopes of postal card or letter sheets is kept. Postmarks are typically dated from days to many months after the date of issuance. An envelope...
Found on http://en.wikipedia.org/wiki/Earliest_reported_postmark
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