Fields: The sheets with the undeveloped strip were quite possibly 3-1/4 x 4-1/4 pack film, and the mix of edge markings suggests the late 1940s or early 1950s. That format, in film pack rather than roll, in turn suggests either a field-type view camera or something from the Graflex family. (It's been a long time, but I think the extra 1/8 on the long dimension is to allow a full 4-1/4 field beyond the adhesive.)

Having just sorted through a lot of old film from the same period, I can vouch for the fact that any 35mm film base that has turned a deep yellowish brown is likely to be nitrate, unless it is clearly marked "safety film". Some of the Kodak Super-XX film that I have is acetate, but not marked "safety", and the Ansco stock is apparently all nitrate. There are a few unopened rolls of Ansco with the date "1949" on the box, and since a car in some of the frames has 1949 license plates, I suspect that the date is that of manufacture, as opposed to expiration.

From the reading that I have done in the last few days, it appears that all roll film is non-nitrate, regardless of date. (I'm curious as to why this would be so.)

The Wikipedia chart is a real resource, but it seems to have been built from industry-standardized "formats" rather than by working forward from a list of cameras. I was delighted to find that three rolls of negatives that I have match one and only one format---121--which was discontinued in 1941. The images are of postwar Occupied Japan, which fits, but I wish I knew what camera would have made them.

I applaud your efforts, and hope that you make some effort to preserve the images, preferably by making silver-gelatin prints. Historians of the future will probably lament the twenty-year void in pictorial history that spans the adoption of digital through the appearance of a practical, archival digital storage method.