The Merrill Lynch Puttable FLOATs/RITES Trust puttable floating option tax-exempt receipts series PT-1506, relating to Philadelphia GO bonds series 2001, is rated 'AAA/A-1+'. The long-term component of the rating is based on the FSA-insured underlying bond. The short-term component of the rating is based on a liquidity guarantee from Merrill Lynch&Co. Inc., and the expiration date of the liquidity facility is Sept. 15, 2003. The short-term component of the rating is on CreditWatch with negative implications because Merrill Lynch&Co. Inc. was placed on CreditWatch with negative implications on Aug. 15, 2002. The Merrill Lynch Puttable FLOATs/RITES Trust residual interest tax-exempt securities receipts series PT-1506, relating to Philadelphia GO bonds series 2001, is rated 'AAA'. The rating