Sweet fancy Moses, I'm in love.
A kind emailer sent over a link to Tommy's Pack Fillers , a company that specializes in reproductions of almost everything related to World War One. You name it and they probably have it- documents, ration labels, weapons, booklets, military ephemera, and the list goes on and on. The usefulness of props like this for WWI "Call of Cthulhu" games is obvious, but even post-war scenarios could benefit from their use.
A selection of paperwork and military ephemera that would be perfect background material for characters that fought in the war. Look no further than Lovecraft's "The Temple" and "Herbert West: Reanimator" for how the Mythos touched on the conflict.
Period matchboxes. I love small props like this not only for their immersive value, but for the attractiveness of the designs.
I know that fighting the Mythos isn't a matter of firepower, but there are times when a case of surplus grenades would certainly come in handy. Just imagine the glee of players stumbling across a crate like this during a game.
Browse around the site and you're sure to find something useful. Personally, I'm going to be ordering a few of the "Fitzroy Compressed Corned Beef" labels for my "From the Mountains of Madness" project. And a grenade or two. And some paybooks. And some weapon's manuals.