Zero-coupon bonds that were created and issued by broker/dealers before the U.S. Department of the Treasury started its STRIPS program in 1985. Zero-coupon bonds are sold at a steep discount and do not pay periodic interest. Instead, the entire principal amount is returned to the bond holder upon maturity. The STRIPS program (Separate Trading of Registered Interest and Principal of Securities) that the Treasury has allows broker/dealers to strip Treasury securities into their component parts. The securities that result are called STRIPS.
Each individual broker/dealer gave its receipt zeros a name. CATS (Certificates of Accrual of Treasury Securities) were issued by Salomon Brothers, which is now part of Citigroup Inc. ETRs (Easy-growth Treasury Receipts) are issued by Dean Witter Reynolds Inc., which is now part of Morgan Stanley. TRs (Treasury Receipts) are generic receipt zeros.