Of all the big hardstone at that auction, that is the one that really caught my eye.
I was thinking it was a big Mano/grinding stone. You see that shape develop on manos right before they are discarded on certain types of metates, but I really think that light groove was for hafting. And the usewear/polish isn't consistent with a mano/grinder. Personally, I think you have a massive ax like tool of some type. Maybe busting/cutting ice on the river? Smashing/fracturing multiple bison bones?
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My thoughts as well as far as not being a mano, the bevel shows wear from forming, and not the area normally doing the grinding.....
All of those large similar pieces I have show that polish on the very ends. A couple are very thin, and I am thinking possibly hoes on them, as the bits show more hard duty type wear around the polished ends.
Remember that nice poled celt with what looked like a mortar patch? I don't know if you heard the end of that discussion, but it turned out that was an Omar that hadn't dislodged or wore out. First one of those I've ever seen.
The mano's you show remind me of one I picked up in Az a few years ago, especially the one on the left.