3 pounder Hotchkiss
Starting from the top
The asterisk preceding the II denotes that this is a Mk II case that has been modified, in relation to 3 & 6 pdrs this means that the primer hole has been rebushed or converted from a cap recess.
The encircled A and following punch mark denotes the case has, subsequent to manufacture, received high temperature annealing. Each subsequent annealing should be denoted by a punch mark, but this case only appears to have one.
The D31 and U38 are the year and lot numbers of the high temperature annealing. Without knowing how much of the alphabet they used, it’s a bit difficult to accurately date, D is about 1913 but U is 1930.
C F F. This is the life of the case. For this period, without going into too greater detail, cases had a maximum life of 6 equivalent full charges of smokeless propellant. For this period, the C can be taken to represent Cordite (it’s more complicated than that) The F denotes how many Full charges the case has had. The first F appears to have been barred out, if that is the case, it denotes for whatever reason the round has been broken down and the propellant removed.
The N as previously stated denotes it is a Naval store.