Complex sentence: Early versions are marked "Nippon Kogaku Japan" and have their focal lengths stated in centimetres, but models produced after about 1965 have focal lengths stated in millimetres and the "Nippon Kogaku Japan" engraved was replaced by "Nikon" from 1971 onwards.
Split into simpler sentences: Early versions are marked "Nippon Kogaku Japan" and have their focal lengths stated in centimetres, but models produced after about 1965 have focal lengths stated in millimetres. The "Nippon Kogaku Japan" engraved was replaced by "Nikon" from 1971 onwards.