Vintage chunky black glass button, with stamped wavy line and rim highlighted in gold lustre. Flat back also coated in gold lustre. Metal back plate and metal loop shank. Backstamped: GLASS DEVELOPMENTS LTD, LONDON. Bimini type but made by a rival company in the mid 20th century.

Size 1.2” (3.3 cm) and irregular shape means it sticks in the large loop - so NBS Large size.