Not much is known about this brooch. It doesn't look like a fern to me from the photos, what I think is this brooch is described by Leslie Field as "a floral spray looped around an enormous pearl" but no further information is given.

My list of wearings that I have for this brooch are:
12th May 1974 - Windsor horse show
11th May 1980 - Windsor horse show
1984 - Jordan state visit
31st May 1987 - Polo Windsor
11th Oct 1989 - Singapore
1992 - Hampton Court flower show

Unfortunately it seems to have been forgotten about after 1992 which is a shame!