Thanks for all the ideas. The consensus seems to be that I'm in the wrong place; I should have posted on the Ethnographic Kitchen Implements forum. Now I'm even happier I didn't bid.
I was glad to see Tim Simmons' answer, and immediately did an image search for "Somali sugar adze." That turns up four images of exactly the right thing so it would seem confirmed. Unfortunately those four images are from Tim Simmons' own post on a past thread on vikingsword saying it's a Somali sugar adze, so it's a bit circular as confirmations go.
LOHAR - Solving The Mistery
Tim, do you recall where you heard/read this?
I can find plenty of pictures of Tuareg sugar hammers, now that I know there is such a thing. They all seem pretty similar to each other in design, and while I can see similarities they're sufficiently different from this weird thing to make me think this is from a different culture, time, or place. Particularly the deer and bird ornamentation. Now that I've seen three different ones, it makes me more convinced that these are a particular tool, rather than a crazy one-off from from mad artisan.
But if there's limited interest in discussing this non-weapon, I'm regardless pleased to think of it as a sugar hammer.