Original: In 1985, Noble Affiliates spun off its subsidiary Noble Drilling Corporation to shareholders, and that company in turn went public by the early 1990s, and then became Noble Corporation, an S&P 500 company.
Simplified: In 1985, Noble Affiliates started its subsidiary Noble Drilling Corporation to shareholders, and that company in turn went public by the early 1990s, and then became Noble Corporation, an S&P 500 company.