What in the OHM are these

Got these in a bag of fired an un-fired cannon primers along with a tool blank.
There are two slotted head screws 180º apart at the black, glossy painted mouth and the “primer” has black insulation around it. Are these some sort of an electric resistance check? For what?
I can only think OHM is a measured rate of electrical resistance. And I’m not sure it would be for a gun. Brass, non-magnetic, about 2 inches long and .48" measured under the rim.

Could it be a specialized fuse?

We used combination lock primers in 16" guns. They could be fired electrically or percussion. Firing locks were kept scrupulously clean and checked with a ‘megger’, an ohm-meter that generated a larger amount of juice, as compared to a Simpson 260 multi-meter. I never saw devices, as in your photo. They might have been an easier way to test the locks. I recall an instance when we had an electrical misfire on the right gun. The poor gun captain had to hook a lanyard to the firing lock for percussion fire. We waited quite a while with our misfire procedures, but, stepping out on a platform behind a loaded gun that misfired must have been excruciating.

Your having the same train of thought I had, but they sure do look like something for a test fixture. Of perhaps for a smaller caliber, or perhaps in testing primers, or perhaps none of the above but entirely different,

Also i just notice there are two slotted head screws 180º apart at the mouth, & not just one as posted but now corrected above.

Thanks for the thoughts, A fuse is something designed to fail when the amperage (the juice) exceeds it’s limits, and is marked in Amps. A resistor (measured in Ohm’s) is designed to slow down if you will, or choke the supply of electrons passing through it.