That is a screw plate used to form threads in malleable material, such as wrought iron.
It does NOT cut threads but swedges them, or forms them.
Commonly used by metalsmiths of all kind prior to the Civil War.
Jewelers and watchsmiths still use them some even today.
This particular one has sizes that would be found in a machine shop for general use.
Nuts would have been custom made, (by a similar process), to fit.