In contrast to qiang spearheads, these were made with an emphasis to powerful thrusting while the qiang type was more versatile and could also be used for cutting. Most qiang are often leaf shaped but some even had hooks or other more unorthodox shapes. Mao seem to be characterized by a comparatively thick and narrow blade with less emphasis on sharp cutting edges.
It would seem to me that mao would be the weapon of choice against armor and for cavalrymen for which it was hard to use a spear for anything else than the thrust. Qiang type spearheads would be excellent for infantry fighting lightly armored or unarmored men. When horses and armor got largely obsolete it is no surprise that most late Qing spearheads encountered appear to be of the qiang type while in Tibet where armor for man and horse was carried up until the 20th century the qiang style spearhead never seemed to have gained popularity.
After a polishing job by Philip Tom this particular spearhead showed an odd steel "insert" at the tip, not covering the edges but running obliquely through it and showing at both "flats" on either side of it's blade.
I showed it to Andrew Jordan, a fine bladesmith that had studied making Japanese swords in Japan for two years and who currently studies and reproduces the particular construction features of edged weapons from around the world. (http://www.jordanknives.com)
He thought the insert was done purposefully, and had seen the feature on a number of Japanese made Yari as well. He thought it had to do with armor piercing. (Where a strong tip was more important than hardened edges for cutting.)
Although hard to date with certainty, I think this spear could well be an 18th century spearhead dating from the time when armor like mail was still used on the battlefields. This spearhead has a nicely engraved brass sleeve with floral designs.
See pictures:
Overall
Insert
Sleeve
-Peter
