I have one very similar to the one on the far right. I got it from Herb Woodend in the mid-1970s. My impression is that it was military but I don't remember what Herb said about it at the time, if anything. I also have two with flat bottom "primer pocket" holes, but of significantly different depths and different bullet ogives. I also have two steel dummies with the same drill point depression as the brass one on your far right, but of different depths. These also go back to the mid-1970s. I think this dates them before much of the enactor activity and before the replica pistols.
During at least the early stages of WWII, the British Army/Home Guard units appear to have made all kinds of dummy rounds. Illustrated are three WRA 9M-M headstamped dummy rounds that came from the UK (the round at far left is a steel case experimental). The second round from right has the HP pictured. All three of these dummies are pretty roughly made. I have seen a number of the two middle rounds. Opinions when I found them, again in the UK in the mid-1970s, was they were probably made up by or for the Home Guard. I suspect the same origin for the unmarked steel and brass dummies I have and for those pictured at the beginning of this thread. Likely very little effort to make sure all the primer pockets were drilled to the same depth or that the bullet ogives matched, or perhaps multiple sources.
Just one opinion.
Cheers,
Lew