I thought the threads on my Krag barrel were lathe cut. Dragged the old barrel out and looked at it with a 7 power loop and I am not sure. Some of the marks look like conventional single point lathe turning and some look like they could be milled as described along with the figure 12 of a thread milling machine.
I thought thread milling was a later invention. Live and learn. Even if this is not the Krag operation described it is very informative as to what was being done in that time period.