This is the cover of an envelope used to hold large photographic negatives (in this case measuring 3-1/2” x 5-3/4”) and the prints, after developing. Dating to the 1910s, based on the subject matter of the negatives, information printed inside noted that Marshall Field & Company charged 10 cents to develop a roll of film and $1.00 for an 8 x 10 enlargement. Regarding the services provided, the envelope states “Our photographic workroom is equipped with the most excellent facilities for developing and printing, the making of negatives, transparencies and lantern slides. Bromide and carbon enlargements.”