Final answer:
The question seems to refer to Van Cleef & Arpels for the creation of a piece for the Shah's wife, not Tiffany & Co., which was associated with Louis Comfort Tiffany, known for his glasswork and not the mentioned emerald piece.
Step-by-step explanation:
The firm formed when he married Estelle Arpels created a piece for the Shah's wife is Van Cleef & Arpels. However, Louis Comfort Tiffany, known for his work with glass and founder of Tiffany & Co., is not associated with creating the mentioned 150-carat engraved emerald. While Tiffany & Co. was established by his father and is famous for jewelry, Louis Comfort Tiffany's career greatly revolved around interior design, glasswork, and particularly his unique stained glass windows.