Those 400 slides are briefly mentioned but seemed forgotten, but I believe that they could hold the key to this enigma. What are the images depicted? This could give us a pretty good range of time based on what images are actually depicted. Do those slides show a time range from 1940 to 1960 based on content? Do these photos give a possible clue as who was the actual photographer and when and where were they processed? Were they processed in bulk or a few at a time? A lot of questions that could be answered.
Based on a few of the slides that have been released, there is one that depicts Ike Eisenhower standing next to Milton Eisenhower on the back of a rail car. Tim Printy put this photo at roughly 1945. This one photo had caused a slight rush that it might have been Bernerd Ray standing next to Ike, but Printy's analysis sunk that inane theory by clearly identifying Milton Eisenhower.
But that is one example of one photograph. What of the others. Yes, let Maussan et al show the two slides allegedly depicting aliens on May 5th, but the real answers may come from the heavy scrutiny of the 400 slides.
Just a thought.