OLDWICK, N.J.--(BUSINESS WIRE)--A.M. Best has revised the outlook to stable from negative and affirmed the financial strength rating (FSR) of A- (Excellent) and the issuer credit ratings (ICR) of "a-" of Pennsylvania National Mutual Casualty Insurance Company (Penn Mutual) and its subsidiaries, Penn National Security Insurance Company, Founders Insurance Company and Partners Mutual Insurance Company (collectively referred to as Penn National Insurance Companies). Concurrently, A.M. Best has aff