Your box was manufactured by BMB - Briggs Motor Bodies Ltd., Dagenham, Essex. They had originally manufactured car bodies for a number of manufacturers but in 1953 were purchased by Ford (UK), which is hardly surprising as they are also in Dagenham.
It would appear the box has been filled at least twice 73 and 77.
The rounds were filled and assembled at R.O.F. (Royal Ordnance Factory) Chorley, Lancashire. “.C.Y.”
The links were manufactured by R.O.F. Radway Green “R.G.” The ADEN cannon can be configured to feed from left or right, so the links are ambidextrous. Just rotate them 180 degrees. Hence, the box being marked “L.H. Feed”.
The NSN 1305-00-255-6315 was a surprise, as I would have thought the UK would have codified the store long before we started supplying the U.S. The “Manufacturer” is shown as “Naval Air Systems Command” which I understand to be the procurement body for the U.S.N.