...+ National Securities Clearing Corp. is planning to issue $4 billion of commercial paper and $1 billion of extendible notes to facilitate the settlement of transactions in the event of a clearing member default. + We are assigning our 'A-1+' rating to the company's commercial paper and our '##+' rating to the extendible notes. + We have also affirmed our '##+'/'A-1+' issuer credit ratings on the company. + The outlook remains stable, reflecting our expectations that National Securities and Clearing Corp.'s financial safeguards will continue to provide substantial protection against member default. NEW YORK (Standard & Poor's) May 26, 2015--Standard & Poor's Ratings Services said today it assigned its 'A-1+' issue credit rating to National Securities Clearing Corp.'s (NSCC) proposed $4 billion of commercial paper and its '##+' rating to the company's $1 billion of extendible notes. At the same time, we affirmed our '##+/A-1+' long- and short-term issuer credit ratings on the company. The...