Likely someone wanted a separate taper-crimp die to add to their three-die set and whipped one up to order. The threads look like they were cut with a die instead bring single-pointed on a lathe or roll-forged, maybe someone had a big threading die handy or turned and threaded it on their lunch break at the Navy machine shop or any number of other scenarios. Maybe it was someone's high-school shop project demonstrating accurate thread form/fit, knurling, parting, boring to a spec, horizontal mill operation to slit on center (missed it by a little), grinding curved form tools, etc. Would be a heck of a semester final project.
Anyway, it's unique, useful, and looks well made.