Paragraph 18017 in WO List of Changes describes the "Plug, fuze-hole, transit, 2-inch, Wood, Marks I and II" and also the "Armilite" Mark I and "Pluton" Mark I.
The wood plugs were made of boxwood or a similar hard wood; the Mark I had a flanged head with slot for key No.48 and the Mark II a .25-inch hole bored diametrically through the top instead of a slot. The two marks were used for plugging empty shell for transit purposes.
The "Armilite" was made of a hard black material called armilite, with a metal-bushed key slot. The plug was "an alternative to steel, iron or metal plugs for transit of heavy shrapnel shell overseas to England". This suggests that the origin of the shell was Canada or the US.
The "Pluton" was similar to the "Armilite" but of different composition and different shape and dimensions. It was used as "an alternative to wood or 'armilite' transit plugs in empty HE and shrapnel shell".
Contracts were generally placed with the Area Munitions Committees for them to distribute to smaller firms, or otherwise directly with largescale wood workers such as bobbin makers. Some random examples shown below: