When Howard Hill made his original heads, they had a parallel ferrule, and he used a rivet to secure them to the shaft. Early field points and target points were also parallel. They were crimped.
The problem with the old parallel tips was finding wood shafts that would fit tight. Wood shafts were not consistently round or of the same diameter, and glue was never strong enough to keep the head on the shaft if it found a tree. So either crimping or rivets were used.
Tapered points came on the market in the late 50's or 60's and solved many of the problems and ferrule cement used in rod building was used to secure tapered points. This was before ferrule-tite came out.
In my opinion, this piece looks homemade, and the front may be solid allowing for the taper. The parallel section would be required for glass unless you had inserts. Only an old-timer would think or it. He probably used them on wood shafts as well.
My question is, is this two pieces? A parallel tube with an tapered insert?
This device would add strength to the glass shaft, which had a tendency to split or fracture with the old style inserts. Old inserts were short, and easily driven back into a shaft if something hard was hit.
Today, there are weighted brass inserts, and steel inserts to increase weight, in aluminum when using a light field point or broadhead, but I don't think it was the original purpose. It looks like a carry-over that someone was accustom to using. This is based on my experience.