A Barcoded Serial Number List (SNL) is used whenever the quantity of SNs or UIDs in a container exceeds five. Mil-Std-129 requires that serial numbers of items be listed on container labels, including those of UIDs. The serial number of the UID/IUID is used because the UII itself can be far too long to effectively list on labels. This is in addition to list the UIIs and their serial numbers in the two-dimensional PDF417 symbol on those labels.
The phrase “SERIAL NUMBER LIST INSIDE” is substituted in place of the serial numbers on the label when the barcoded list is used for serial numbered items. “SER NO UID LIST INSIDE” is used when the serialized items are IUIDs. “Copies of the list(s) shall be placed inside and outside a container.” [Mil-Std-129R 18.104.22.168.1.c.1]
There are other uses of the SNL beyond the Mil-Std-129 requirement. Some contractors (and their customers) use a combined list of all serial numbers / UIDs shipped, organized per line item. This can be useful for those handling the shipment and for shipment records.
The serial number list is an extension of the label format, using a linear barcode for each serial number or UID-SN in the container. This allows the serialized data to be collected using simple wands or linear scanners.
Each SN or Unique Item Identifier (UII) SN is included in a two-dimensional PDF417 symbol for the items listed on each page. In the same way that the simple linear barcodes are useful to people scanning the list, the PDF417 is useful to automated identification systems. The data encoded in the PDF417 includes formal data identifiers for the UIIs and/or SNs allowing automated systems to gather up all of the data in a single read. The identification data from the container label is also included, providing robust information about the contents of container.