Well if it is a hobble, it wasn't put to use yet. There is no sign of any wear. It was pecked to shape, and never polished.
gb...I don't think a few decades of slamming into ice would put much at all for wear marks on it. There is enough current the ice doesn't get real think, in fact it isn't completely frozen over very often at all. AND, they didn't have to get through 2 foot of ice, like we do in the lakes to ice fish in the dead of winter.
Anyway, who knows, it is just a simple theory I have had for a while now, just because of the lack of use wear, And where it was found. The stretch of river was known to be heavily used by the natives for swimming, bathing and washing. (I have some older neighbors who's grandparents, the homesteaders remember the natives living nearby, and that is the story.) So I suspect they needed access to the water at times when it was hard on top. A big rock is the best thing I can think of for getting through some river ice. I also understand the need to have a provision for attaching a rope to it, hence the 3/4 groove
