If your device were a ram/cleaning rod, the existing threaded end would be to extend a second (and even a third) section and then a final threaded end, often narrower than the sectional ones, would be for the application of a male extraction worm, a cleaning brush or other.
Still the dimension of the so called grip in yours would be too big for the operation.
Something doesn't square here, or this is an atypical specimen, at least to my non experienced eyes.
Attached are examples of 20th century shotgun kits and a replica of a 19th century pistol rod, some time shortened.
Your device, far from being an ancient accouterment, should be comparable to these, i guess
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