1/10 12KGF: This stands for Gold Filled. It means that 10% (1/10th) of the total weight of the metal parts consists of 12-karat gold bonded to a base metal. Unlike thin gold plating, gold-filled frames feature a thick layer of gold that offers long-lasting durability against rust and wear. S.R.O.: This is the maker's hallmark for Styl-Rite Optical, a highly popular American eyewear manufacturer that produced high-quality frames during the mid-20th century. 20: This denotes a 20mm bridge width, which is the distance between the two lenses across your nose. Style and History These are iconic 1950s "combination" cat-eye glasses. They combine acetate or aluminum upper brow bars with gold-filled lower rims and chassis. The delicate leaf filigree detailing on the wingtips is classic Mid-Century Modern styling. In excellent condition..very little visible damage or wear, especially for their age.