Cotton canvas US military belt bag, used but in very usable condition yet. I've shown this with my phone and multi-tool (not included) to give you an idea as to the scale here. This is well sized for a GPS or radio or camera, or a small tool kit.
The pouch measures 3" wide x 2", 6 1/2" deep, about 8 1/2" tall under the cover. I'm uncertain as to the exact age of this piece, military gear isn't really my specialty!