See attachments for a theory of these artifacts being fasteners for a strap to the Sextant box.
What photo is that a detail from?
The larger image was taken from the online Purdue Archives,
image #63"Amelia Earhart underneath he wing of the Electra"
Zoomed in on it before saving a copy. I think it shows the thread pattern and a possible button or gasket over the smaller hole better than the other images.
It's the box (likely a tool box) to the far left.
The smaller image at the bottom left of the pdf is the same image but a 300dpi copy ordered.
I also ordered their old 600 dpi scan they had on file and ordered a new 600dpi scan but they both came out with too much contrast in that area. I attached the 300 dpi image to the pdf because I beleive it showed what may be teeth better and the screw looks like it has a rounded head and looks off center, similar to the artifact.
What I think is similar is the rounded head screw in one hole and a radial, or fan stitch pattern in the other. It may be more of a similar method of attaching straps to boxes so they can both be carried and then anchored to the plane than an exact match.