Yep, got there in the end! Should have spotted the link there before really! They appear to be quite a hefty piece of kit compared to more modern launchers found on the AK series say.
Cup launchers and pole rifle grenades quickly gave way to the muzzle launchers found first on US rifles, and then later on weapons in the Soviet sphere, at the end of the Second World War. At least this is how I see it, since the US was sporting such launchers during the interwar period and the Second World War, while others using rifle grenades were using one of the other two types (or both) described.