Henry Dreyfuss designed the style 6 case for the Big and Baby Bens, and they were introduced to the market in 1949. Notice the new style of hands and that the entire number 12 is printed on the dial (previous styles had only a partial 12 due to the alarm dial).
Style 6 Baby Bens were made in gunmetal cases with nickel trim, and ivory cases with brass trim. Gunmetal cases have a white dial with black numerals or a black dial with luminous numerals. Ivory cases have either a white dial with brown numerals or a brown dial with luminous numerals.
Almost all Baby Ben movements were nickel plated up to 1951.
This design was not patented. It is unknown if a patent was actually applied for or why a patent wasn’t pursued. Perhaps the design of Style 6 was too similar to Style 5 and was not considered worth the expenditure to go after a patent.