...as we recently were, here and here, JTG brought up the Stokes Mortar and its round, so I thought I would poke through the Holdings, and see what we had. This is the result! JTG mentioned the Stokes Mortar of WWI, details of which are available here and here. I would note that Sir Wilfred pretty much got it right the first time - just about everything since has been tweaks. The Wikipedia article has a photograph with a projectile of the type in the Holdings. As you can see, the Stokes round is...