The BOCN forum list is based on a small selection of official documents dated from around WWII. Its all my own work and thanks for the plug Local Chap
I can't tell you much about the wooden boxes but the 81mm mortar box is a B192 mk I. Obsolete in British service now, the mk II superseded it.
Each box has a letter/number code which identifies what it is. It will also have a manufacture date and the initials of the manufacturer.
The 12pr box is Naval, see the large N stamped into the end? W80 is the box code. A large N and the code identifier on the end of the box are typical indicators of Naval boxes. Check to see if there is any Cream coloured paint underneath the brown.