Ok , I'm still actively engaged here , and to those who responded to my plea for information ( and those of the other two ) Thank You !
however , I must say , the information was so murky - really vague in fact ! which begs my question - How is it that so many responders
are over the moon for this ?, when by your own admission, nobody is really confident about what this is, what it means , what the use
was - pragmatic/ shamanic / ? Can somebody please give me some information here ? Am I the only one who is mystified here - really
Unfortunately you're never going to get an answer that gives you the exact use. There are no records of these items being used which is why they are called prehistoric. Much of the reason we know how some of the Native Americans used items is because of the accounts of early Spanish explorers in the Americas. They detailed accounts of how artifacts were being used to some extent. However, in the case of bar amulets and birdstones, their use had long since disappeared by the time the Spanish were exploring. Why their use disappeared is as much of a mystery as how they were used. Apparently the traditions weren't adopted by the next culture for some reason.
Okay, now that we're clear on that, I'll give you a few schools of thought for their use. Some believe they were either used as handles or weights for the atlatl. The atlatl is the ancient spear throwing "machine" which consisted of a foreshaft, a shaft, a handle, a hook, and probably a bannerstone or some other weight. They used weights on the atlatl to increase the force applied when swinging hte atlatl. It's simple physics that applying weight to the moment arm will increase the velocity of the spear. Experimental archaeology shows that adding weight has an impact to velocity. Also, since bannerstones were found in context with buried atlatl hooks which lead to the conclusion that adding weight was needed. Anyway, back to the bar amulet; it's been theorized that the holes in the end of the bar were for suspension to the atlatl. Or, since the shape of the amulet is somewhat like a handle, they were used as a handle for the atlatl. To my knowledge, there hasn't been a bar amulet recovered in a good enough context to make a better judgement for their use. They are attributed to a culture that only lasted for a short time (maybe 500 years) so there's not a lot of evidence to go on.
The reason they are called bar amulets is because early collectors often theorized about their use and assigned names to objects. The collectors knew they were Indian and the most functional thing they could come up with is they were used for jewely or charms which lead them to the name amulet. An amulet, by definition, is a charm or ornament often worn around the neck sometimes thought to ward off evil or injury. There could be some creedence to the idea of them being jewelry as the holes often show wear from being tied on to something. After wearing one of these as jewelry in the movement of the amulet on a string would cause wear in the holes.
In summary, you're never going to get a definitive answer to their use. Why are they so rare? Well, honestly, there weren't many of them made. In contrast to coins which have records of quantity of production, there are no records for these items. No one knows how many exist. I probably know hundreds if not thousands of collectors and I have only known 3 people that have found one whole or broken. Maybe that will give you some idea of their rarity. Now speaking for value, even a small hardstone bar amulet is quite valuable. A friend of mine has two that he purchased that are smaller and not as well made and he's asking $2500 each for them. Also, a friend of mine owned the best hardstone bar amulet known to be found and he let that one go for $10,000. I don't think you could buy it back now for anything under $15k.
Hopefully that gives you some idea of use, rarity, and value. Value is highly subjective and out of respect I wont begin to try and assign a value to Jonzer's find. I'll just say that I would love to have it!!!!!
Here's a link to another picture of one made of slate:
http://www.nmai.si.edu/searchcollec...811&objtype=Hunting/Fishing/Warfare&objid=Bar amulet (throwing stick/atlatl weight)
Hippy
on making a well deserved BANNER. 
