The Frers relationship with Nautor’s Swan started 1980. He designed the 51 and the 651, then in 1983 he designed the 46 “considered one of the most successful designs ever carried out by the Frers/Nautor team”.

With 109 hulls built and sold it still remains the largest volume design of the entire range.
Swan 46 MKI produced from 1982 to 1990 – 81 hulls
Swan 46 MKII produced from 1990 to 1997 – 28 hulls

The Series Date for an IRC certificate for a Swan 46 MKI and a Swan 46 MKII should both be the same 1983.