Complex sentence: An estate car joined the range in May 1962, and a two door convertible in June 1962: the convertible never sold in significant numbers and had been dropped from the range by the introduction, in September 1964, of the Super Minx series 3.
Split into simpler sentences: An estate car joined the range in May 1962, and a two door convertible in June 1962. The convertible never sold in significant numbers: the last one was made in June 1964, ahead of the introduction, in September 1964, of the Super Minx series 3.