This 10-ounce clear glass bottle is a beautiful relic from the "Golden Age" of home darkroom processing. Embossed with the "Eastman Kodak Co. Tested Chemicals" seal and the iconic "EK" logo, these bottles were used to sell high-purity raw chemicals (like Hydroquinone or Sodium Thiosulfate) back when photographers often mixed their own developers and fixers from scratch. This specific unit features graduated measurement markings on the side (2, 4, 6, 8 oz) and shows a distinctive yellow/amber residue at the bottom. In photographic history, this residue is often the result of sulfur precipitation from old fixer or the oxidation of developer components over nearly a century. It serves as a literal "time capsule" of the chemistry that once brought images to life.