It depends a great deal on the subject matter and the historical value as well as the photographer if known. Look for military, industrial, native american, old west. sports, advertising, landscapes and nature to name a several good subjects. Portraits of unknown regular people are not as desirable. A huge collection of Ansul Adams glass negatives was discovered years ago used to build a greenhouse. They were extremely valuable. You never know what you may have there. You need to look at every single one. I am very interested to know what you find. You may have some real history there.
