Second series (late 1958-1962, 1958-1959 cars are often called 'intermediate'):
GAZ M21A - taxi (the same index as for the first series taxi),
GAZ M21I (М21И) - basic modification,
GAZ M21K - export modification,
GAZ M21KB (М21КБ) - cars for Belgium,
GAZ M21KJu (М21КЮ) - M21K for tropical countries,
GAZ M21U (М21У) - lux modification.
Second series can be recognized from the outside by a grille with 16 wide vertical vents ('shark jaws').
Photo from Wikipedia also.