To be eligible paper, the issue must carry one of the two highest ratings ("1" or "2") from at least two of the credit rating companies. Tier-1 paper is defined as eligible paper that is rated "T' by...

To be eligible paper, the issue must carry one of the two highest ratings ("1" or "2") from at least two of the credit rating companies. Tier-1 paper is defined as eligible paper that is rated "T' by at least two of the rating agencies; tier-2 paper security is defined as eligible paper that is not a tier-1 security.