From John Simmonds' book, but with my comments in square brackets: 1979 to [sometime in] 1981 Willie Manson was not at Caithness Glass. He had a venture called William Manson Paperweights in Ayrshire. After rejoining [or working as a freelance at
] Caithness Glass in 1981 he stayed until 1997 when William Manson Paperweights was reborn. The book has other relevant details, too, which are not in the SG page.