The meter serial number (also referred to as the meter number) is the identification number registered with the USPS for the postage meter license. This number shows on the indicia and on the identification tag on the back of the meter.
The indicia shows the seven digit meter serial number along with postage paid, the date, and origin location.
The identification (ID) tag on back of the meter also shows the meter serial number along with the Product Code Number (PCN), such as K700 or K7M0.
UPDATED: April 07, 2016