BSK Amethyst Brooch Shop » Costume Estate Jewellery » BSK Amethyst Brooch BSK Amethyst Brooch Vintage 'BSK' Stylized Leaf Brooch w/ Stunning Faux Amethyst $35.00 1 Simple gold plated design with a huge, freeform faceted amethyst-colour glass. It measures 7cm x 5.5cm.A New York manufacturer during the 1940-1950’s.