I just bought a C 3 new in the box, it came with 2 filters that fit the 50mm lens, the film canaster is likely for loading your film. My C 3 is new and I dont think it was ever used, I need to get the shutter services and the 50mm needs to lubed it is tight.
actually, no, this will not work in M-series cameras. It has a blackknob (that thing sticking out on top) which means it was made for the screw mount cameras of earlier vintage.
M-series cameras use a very similar cassette with a chrome (silver) knob on top. This is too tall to fit in an M-camera and will not work, but a chrome knob one will work in a barnack camera.
Sadly, a leica cassette of any vintage will not work in an Argus.