Secret Stuff in Bar Codes, Part 2:
Dates, Issues, Variants, and Printings

In the EAN13 and UPC-A barcode formats used on most comics today, there are either two or five digits at the right in shorter bars which are called the “supplemental”. But what do those numbers mean?

When the supplemental is just two digits long, as was common on books throughout the 1980s, the digits convey the cover month. E.g. “05” is May, “12” is December, etc. Unfortunately, it was common in the early days of barcoding comic books to recycle those numbers every 12 months without changing the main barcode. As a result, there are any number of comics from the 1980s who share barcodes with the issue twelve numbers before it.

More recently (since about 1993), most comic companies switched to a five digit supplemental which is (or at least should be) unique to that comic.


The first three digits of the supplemental are the issue number (here, issue #001). The next digit—at least as is used with comics—is the variant. Simply by looking at this digit, an eagle-eyed indexer can tell that this is the second variant of this comic (a “1” would signify the regular edition). The last digit is the printing number (here, “1” meaning first printing).

Unfortunately, getting the last five digits right is up to the publisher, and the folks in charge of producing variant covers don’t always sync up with the folks who generate the barcodes. As a result, it’s very common to issue any number of variants and multiple printings without updating the barcode. Essentially, it tells you something when the barcode shows numbers other than “1” for the last two digits, but it don’t necessarily treat them as authoritative when it comes to deciding whether something is a variant or second printing.