Here's the concept drawing:
I took a few screenshots of work in progress.
Started with a box and extruded a ridge in one corner.
Cropped to just the corner faces.
Split the faces to add handles.
Then half a catch.
Used the mirror modifier to repeat the one corner to make the whole box.
Joined it all together.
Removed unnecessary vertices.
UV Mapped the texture.
Used GIMP to create the texture and kept replacing the one used in Blender.
Added more details.
Nearly finished model.
This will be used as an Ammo case for picking up reloads within the game. It took me all day Sunday to get this far and still needs a little bit more work where the textures have been stretched unevenly.