On Catalogablog there is an posting on Tuesday, September 21, 2004.
From: Code for Libraries [mailto:[log in to unmask]] On Behalf Of
David J. Fiander
Sent: Wednesday, May 01, 2013 10:35 AM
To: [log in to unmask]
Subject: [CODE4LIB] When did OCLC's original xISBN service launch?
According to the Code4Lib mailing list archives, the service moved from
"experimental" to production, and changed format, in February, 2007, but
the earliest reference to the service in the archives is a question from
Thom Hickey in May, 2005 soliciting feedback about what additional
features might be of interest.