Between 1944 and 1945, a US Photo Reconnaissance Squadron or (or something alike) did a survey of the whole Chilean territory using the Trimetrogon camera system (228 rolls of film and about 49.000 photographies). This system consisted of three Fairchild K-17 cameras with 6" Metrogon lenses pointing left, right and down.
I'm a glaciologist doing research using those old images and I'm trying to learn more about the mission that carried out the survey. This is not only out of curiosity, as to do topographic reconstruction I need to resolve the lens distortion parameters and I need to know if all images were taken by a single system in a single plane, or if there were multiple systems involved.
The photographs have markings like this: To interpret these markings a manual of the time gave the example "137PS-3M109-11-V-121" where the information was interpreted as follows (1) 137PS. Photograph made by 137th Photo Reconnaissance Squadron USAAF. (2) 3M109. The year is 1943, indicated by the fourth digit of the calendar year, that is, 3 for 1943. The letter M stands for mission, 109 for the mission number
Therefore, from the information in the picture above, the survey in Chile was done by a unit identified as 91PC but I've been unable to find a Photo or Recognnissance squadron/group/wing or whatever that fits this code (See UPDATE at the end below images). The number "5" stands for year 1945 and 4028 would be the mission number. But I haven't been able to find any information of such mission.
Good progress would be to identify the model of the plane(s) that carried out the survey, but the only clue I have are thousands of pictures porting the tip of the wing. But I don't know if that is possible for such a small clue. Can anyone identify this plane or has any further information about this surveying mission?
Below some examples of images of the wing:
UPDATE: On the Wikipedia page of the 311th Air Division it mentions the "91st Photographic Mapping Squadron (later 91st Photographic Charting Squadron, 91st Reconnaissance Squadron): 5 October 1944 – 26 August 1946". So, 91st Photographic Charting Squadron seems to fit the "91PC", and the dates match too. Anyway I haven't find much details about the missions performed by this squadron, planes used or any other detail.