A sample box demonstrating a shock-proof fabrication in laminated CP3 sheet (Delarin), and using laminated angle mouldings for angle joint reinforcement. The fabrication was intended for use in severe conditions in the British Rail Severn Tunnel. It was required to withstand impact from 10lb lumps of coal being moved at 40mph, a warm steamy sulphurous atmosphere and being splashed with brine from water leaks in the tunnel. The fabricated cabinets were made to contain signal relays and had lift-off front covers. The sample was also used as the basic form of the later submarine battery boxes. A handwritten description of the box and sketch of the corners and joints accompanies this object.