hi Sue,
Taken from Franks Ysart glass site:
"The jewellery was Paul Ysart’s idea. He had been making small ‘stones’ and setting into cheap jewel fittings as presents for friends and family. Caithness saw a potential and put Colin Terris in charge of further development. The range was officially launched in December 1970. Colin Terris designed a range of brooches and pendants inspired by traditional Scottish design and hired Lucia Polanski as a jewellery designer; she produced the rings, earrings and cufflinks designs. "
Also see the link Erhard put in - mine is in a box labelled R20 but like a lot of things - (they were hand written) and not always correct!