Thank you...I'm happy that you're taking a different approach to the solution....
I used a known measurement from my Carcano and compared it to that measurement in the photo, and found that the multiplier for the photo is 16.29. IOW....The box would be 18.7 inches wide.... and the rifle would be 43.5 inches long.
I really need the actual measurement of the box......
The box dimensions are standard 16" x 20" x 14". But you need a ruler of known dimensions within the image to confirm it. You've got it backwards trying to use the box to measure the MC. You must use the known dimensions of the MC to measure the box. Only if the box resolves to a standard size can you use it as a ruler. This will in turn confirm the dimensions of the MC.
Not sure if the image files I linked to will show since they don't for me. My approach is applying photogrammetry which is just measuring 3D objects in 2D photos. Our unit of measurement for images will be pixels which we must convert to a physical unit such as inches. I composed the following image to help you out:
I isolated the areas we intend to measure, doubled the resolution and brightened it up enough to clearly make out the ends of the MC. Fortunately, the rifle is almost orthogonal to the POV so there will be no foreshortening to consider. This occurs when one end of an object is farther away from the camera than the other end which compresses the image. The image length is reduced by the cosine of the angle of the lean away from (or towards) the camera. In this case the lean is negligible so we can take direct measurements of the rifle on the image.
In the image I posted I took measurements from the middle of the buttend to the end of the barrel, to the sights, to the piece that Oswald supposedly smuggled into the TSBD in a paper bag (34"), and to the end of the action at the forend. Then I measured the width of the far end of the box.
Note that I cut and pasted horizontal strips of the measurements at the upper left corner of the image so you can count the pixels for each measurement. Copy and paste this image into MS Paint and hold your cursor at the end of each segment and note the pixel x,y (bottom left corner of Paint). Also note that I placed the measurement of the box as the bottom segment which I denoted with a red bullseye. That is the pixel width for the box. Because it is so close to the rifle, we can assume that both objects occupy the same plane and are commonly scaled.
For example: The rifle part without the barrel which Oswald supposedly smuggled into the TSBD is thought to be 34". In my prev image, that measurement on the MC is 894 pixels long.
This segment is 894 pixels / 34 inches = 26.3 pixels/inch (specific to this image). The box width is 426 pixels (red bullseye) @ 26.3 pixels/inch =
16.2 inches. This tells me that the 34" measurement of the barrelless MC is accurate.
Now it's your turn to measure these lengths (inches) on your own MC for the segments on the image I posted, and calculate the pixels/inch ratios. They should ALL be 26.3 pixels/inch to be an authentic MC as portrayed in the image. Let me know if the rifle matches yours. Otherwise, forget about the box.