jmfg222,
Nice "in production" Banner stone !!
When natives "stopped" during production of a piece, it usually involved discovering a previously hidden "flaw" in the stone, or a unrecoverable mistake during manufacture that has doomed the piece. (Do you see any cracks, flaws in the stone that might have ruined the finish piece?)
The one thing that I see on this piece, that might have been a problem, is that the pecked starter hole seems to be slightly off of center. This may have been to "their" experience an unrecoverable mistake. From this point the hole would have been continued with a hollow reed. The reed would have be spun by hand or with a bow drill. An abrasive like crushed quarts or sand or other, would have be added to the hole to facilitate the drilling. This would leave a cyridical(sp) stone tube inside the reed. (the rock tubes have been found archaeologically) The hole would have been drilled from both sides, and had to meet inside the stone. (that takes some real coordination)
It also may have been that this stone was unwittingly, dropped or lost, or a tragic accident stopped the production of this piece.
Banner stones were added to atlatls as a weight, or "possibly" as a sound damper, during the throwing process. A lot is still unknown about the real function of these stones. They "must" have be really important to the natives, since it required so much work to produce one.
Very nice find !!