Sterling silver Modernist brooch. Vintage 1979 round pin badge with dark purple blue stone, garnet/amethyst cabochon. 1970s, London stamped

A super handmade Sterling silver brooch dating from 1979.
It's stamped on the back with the maker's initials which look like DL, then two assay marks (London, Sterling Silver) with the date stamp of 1979. The stamps are so tiny they're hard to see with the naked eye.

A thin delicate beautiful retro brooch, looks stunning on.
Circular with an inset stone which I'm pretty sure is a dark purple/blue garnet cabochon (polished rounded semi circular stone).
It could also be an amethyst, but I'm no expert on stones, please see photos.
The outer silver edges have a freeform hand-stamped irregular Modernist style pattern.
Textured and lightly undulating silver.

The pin on the back is very handmade in appearance/feel. Works well.

3.3cm wide.