I recently purchased several postcards from the estate of a gentleman who served in the Civil Defense during WW2. Among these were a group of 26 photos that chronologically depict the construction of the Panama Canal. They are 5 1/2" x 4", made of heavy stock and are subtitled at the bottom with a date ranging from 1903 to 1909. The reverse side was completely blank. Any idea what the purpose of these were and it they have any value.
