Many British men wear a signet ring on the little finger of the left hand, which is considered to be the correct place for it.
In common with many American families, in homage to the British tradition, President Roosevelt wore a signet ring handed down to him by his father James, and which was inherited by FDR's son James Roosevelt. All three generations wore the signet on top of their wedding bands, on their left pinkies. FDR's pinky signet was noted and admired by Sir Winston Churchill (who wore his own gold signet on a different finger).
Wedding bands (always a gift from wife to husband) were usually worn by Western men in the Victorian age on the left hand pinky finger, although few British men wore wedding rings until WW II. Because of masculine limitations, men were encouraged to wear a second ring if they desired, but it was to be worn on top of the wedding band so as to keep both rings confined to one finger. It appears the custom for men to wear their two rings on the left pinky was purely British and German; in America, men either followed the British tradition or wore no ring at all until much later.