Investment grade 

the obligation has been determined to be in one of the top four generic lettered rating classifications by a securities rating agency acceptable to the commissioner, that the obligation has been identified in writing by such a rating agency to be of investment grade quality, or, if the obligation has not been submitted to any such rating agency, that the obligation has been determined to be investment grade (Class 1 and Class 2) by the Securities Valuation Office of the National Association of Insurance Commissioners.