Hi Gang,
It seems strange, that the slide mechanism would be on a ridged pole.
I would tend to believe that the slide came from another rig. The ridges would make it a bugger to use, and would be rubbed away in short order, if it would work at all. Oh, nevermind, I just saw that the lower part of the pole IS smooth DEH!
The most 'period' rig I made, was using a split piece of bamboo, that was fitted to an oak pole,re- glued, and hemp tie-banded. It was very smooth, to operate correctly. It did heat up quite a bit with a lot of use. The metal rig would make and easy switch to any yari pole you picked up on the battle field. As long as you could slide it on, and the pole was smooth, you could rock-and-roll.
Plus, it took some time to make. That is likely why they were not widely adapted. But in the hands of a specialized unit that was trained in their use, they would be as effective as an RPG. You could move up and blow a hole in the enemy line in short order.
The blade does look very interesting...
Mark