Hi Chris,
This is an "interchangeable" wheel - its mate on the front would be the same except that the brake drum wouldn't have a sprocket on the outside. By undoing the three long nuts and withdrawing the axle, the brake and chain could stay in place. Norton used this setup from the early thirties until the late forties, but I'm not sure that your wheel is Norton, mostly due to the rather flimsy brake torque anchor. Perhaps other makes/models used a similar setup.
Leon