Vintage Gold Seal Standard of Quality Microscope Cover Glasses. Non-corrosive - will not fog, 1/2 ounce, 24 x 35mm (0.94 x 1.37"), #1 thickness Made in U.S.A. Box contains 20 - 1/2 ounce boxes, all sealed and in original, new, condition. Gold Seal was a prominent, high quality brand in the mid centruty. The date on the back of the box reads, Dec 29 1966. 

"Gold Seal microscope cover glasses, a product of Clay-Adams Company, were a popular choice for pathologists and anatomists due to their quality and reliability. Clay-Adams, initially a manufacturer and importer of medical and laboratory supplies, began producing these cover glasses in their New York City workshops, using glass sourced from the United States. The company was later acquired by Becton, Dickinson and Company in 1964. The Gold Seal brand became synonymous with high-quality microscope slides and cover glasses." ...Google AI