Article 91885 of alt.folklore.urban:
Newsgroups: sci.skeptic,talk.origins,alt.atheism,alt.folklore.urban
From: fstuart@eng.auburn.edu (Frank Stuart)
Subject: Re: Barcodes containing 666
Organization: Sequential
Date: Mon, 17 Jan 1994 13:35:16 GMT

jfurr@acpub.duke.edu (Joel Furr) writes:
>Bruce Stephens <bruce@liverpool.ac.uk> wrote:
>>Can anyone point me to a file describing why barcodes are said to have
>>666 encoded in them.
>>
>>I'm *sure* I've seen the explanation somewhere, but neither the a.f.u.
>>nor the sci.skeptic FAQs appear to have a description.
>>
>>I've set followups to me; I'll post the information when I get some!
>
>It's very simple.
>
>Many Christians refuse to believe anyone who shows them evidence that
>barcodes DO NOT contain the digits '666', preferring faith over logic.

I think this is what you're looking for:

#From: mcelwre@cnsvax.uwec.edu
#Newsgroups: comp.misc
#Subject: MARK-OF-THE-BEA$T bar-code$
#Date: 6 Oct 92 18:03:33 -0600
#Organization: University of Wisconsin Eau Claire
#
#
#                           THE "MARK OF THE BEA$T"
#
#               ALL Christians are PROHIBITED by Revelation 14:9-11 from 
#          cooperating with the "MARK-OF-THE-BEA$T" bar-code, OCR-
#          number, and magnetic-strip scanning systems, (as found in 
#          local libraries, supermarkets, retail establishments, etc.), 
#          which also THREATEN to SUBVERT Individual Privacy and 
#          Freedom. 
#
#               The scanners can serve THE SAME CRIMINAL PURPOSE as the 
#          TV cameras in the book "1984"! 
#
#               The UPC bar-codes are probably the most blatant form of 
#          the "MARK OF THE BEA$T" so far, with the "NUMBER OF THE 
#          BEA$T", 666, ALREADY CODED INTO THEM.  Each of the so-called 
#          "guard patterns", pairs of thin lines spaced close together 
#          at the beginning, middle, and end of each full-length UPC 
#          bar-code, is IDENTICAL to one of the two codes for a 6. 
#
#               WARN YOUR FRIENDS!
#
#
#               UN-altered REPRODUCTION and DISSEMINATION of this 
#          IMPORTANT Information is ENCOURAGED. 
#
#
#                                   Robert E. McElwaine
#
#
#
#

If you check the date, you will see that it was NOT post on 1 Apr.


Frank Stuart           | Jesus died for your sins!
fstuart@eng.auburn.edu | Don't disappoint him.