Variable headspace/OAL device, used for setting up or testing ammuniton loading machinery???
I have made similar devices for testing the Headspace on guns and setting die sets in my progressive presses,for which I don’t have regular ground steel Headspace gauges…mine are a bit different, in that I can lock the setting with a lock screw, then measure the HS distance with a dial caliper.
Just a suggestion from my own experiences, seeing that a number of calibres have been mentioned, all of which have been made by French ammo factories for military use at one time or other…
Regards, a notre cousins francaises,