The financial definition for Lehman Brothers Mortgage Backed Securities Index:
A benchmark index that includes 15- and 30-year fixed-rate securities backed by mortgage pools of the Government National Mortgage Association (GNMA), Federal Home Loan Mortgage Corporation (FHLMC), and Federal National Mortgage Association (FNMA).
Agency securities Securities issued by federally related institutions and U.S. government-sponsored entities. Such agencies were created to reduce borrowing costs for certain sectors of the economy, such as agriculture.
Book entry securities
Book entry securities System in which securities are not represented by paper securities but are maintained in computerized records at the securities in the names of member banks, which in turn keep computer records of the securities they own as well as those they are holding for customers. In the case of other securities where a securities has developed, certificates reside in a central securities or by another securities. These securities do not move from holder to holder.
Certificate of Accrual on Treasury Securities (CATS)