[13 July 2007 update: Replaced broken link to OCLC glossary with a working link, changed the definition so that it's the same as OCLC's updated definition]
There are so many acronyms around - and the same combination of words can mean so many different things, depending on who uses it. So when the new ILL person at my library didn't know what "CCG" meant when it appeared on one of her ILL requests, I assumed that this acronym was born of libraryspeak. Unfortunately, I know of no Biebers (a fine publication which decodes the acronyms for legal publications) for the library world. Instead I turned to the web, and after one false start, I found a very helpful resource done by you know who - Google. I don't know for how long the Google Glossary has been around, but this was the first time that I used it. I entered CCG into its search box and saw my answer in the sixth hit:
A code provided by the Borrower that indicates a request conforms to the Commission on New Technological Uses of Copyright Works (CONTU) guidelines.
This made sense because the request was for a number of chapters from a book, and somebody might wonder if this was going beyond "fair use." Even more obvious was that this came from OCLC - and even a reference librarian knows that OCLC speaks ex cathedra in this area.