PVX: I was a master control operator in the 1990s and 2000s, and the ISCI codes were 4 letters and 4 numbers. An Ad Council public service announcement started with the letter C and three letters for the campaign, the digits would start with the year the spot was created, the revision or version number, and the last 2 digits being the length of the ad, so a 30 second Smokey the Bear Forest Fire Prevention PSA from 1999 would have been CNFF-9130.