PSC - Pressed Steel Company, Cowley, Oxford. At one point manufactured steel body panels for most of the major UK car manufacturers. Perhaps better known for Prestcold Refrigerators.
RPW - Its presence within a rectangle identifies it as a repair station - which one, I don’t know.
1/53 - Probably the date of repair.
2B - No idea.
CFF - This is the case life history, showing it has been filled twice with a full charge “F” of smokeless powder “C” At one point British artillery case were lifed to six equivalent full charges, hence the necessity of recording how many time it had been filled and what with.
15 II - No 15 Mark II Primer.
Q - Primer suitable for Quick firing weapons.
HC - is the manufacturer, whose identity I will need to look up
3VR - Empty series lot number - manufactured sometime in 1943
KBY - Royal Ordnance Factory Kirkby - filling factory of the primer.
Update - HC - Hercules Cycle & Motor Company Ltd., Rocky Lane, Aston, Birmingham