Eva a lot of stereoscopic photographic sets/images have not survived. The Robin Stanford collection (with its extensive collection of Civil War stereoscopic photographs) at the Library of Congress, that I linked to above, was only donated in 2015 - I think, and has photographs of events that we don't seem to have other surviving photographs of.
Link to images:
https://www.loc.gov/pictures/search/?q=r...st=gallery
Link to catalog description:
https://www.loc.gov/pictures/item/2015645331/
Also, Dave mentioned that there were other photos of Fort Jefferson that seemed to be taken at the same time as this one.