While working at Focus Prints in the late 60’s a customer came into the store with a collection of glass negatives. ( Photographic plates preceded photographic film as a capture medium in photography. The light-sensitive emulsion of silver salts was coated on a glass plate usually the night before the shoot The photographer used a heavy camera which needed a tripod because of the long shutter speeds) The customer wanted cheap prints from the plates. I worked at night and used the cheapest paper on hand. Charged him a ridicul;ously low price. He went away happy and I kept copies of what I thought were the most interesting prints. You can find more info of the Gold Rush here.