Antique (1940s, 1950s?) tool that expert can't place. Who knows what this is?

My Grandpa's a bit of a local historian when it comes to antique farm tools. Last summer he bought this one at a flea market in North Carolina, USA. Having grown up on a farm in rural Wisconsin in the 1930s and 40s, he now prides himself on his extensive knowledge of antique tools and farm equipment from that era. In fact, over the years he's developed a collection of more that 100 implements from that era, and even earlier, with the goal of owning one of each of the tools he'd have used as a boy on the farm. From hay knives to wooden-framed block planes, spoke shaves to cow kickers, it's safe to say he's almost completed his collection, save for the odd piece he comes across that he's never seen before. Case in point, this wooden-handled tool that has him scratching his head. The tool is about 17 in. from tip to tip, with a nearly 10 in. curved blade. The five teeth at the end are the only sharp parts of the blade, with the rest having been machined flat. It does appear that the tool was manufactured this way, but Grandpa hasn't ruled out it's having been adapted from a different tool for a specific purpose. Trouble is, we can't figure out what that purpose could be. What do you think? Hand made? Manufactured? And what does it do? http://imgur.com/a/KGkLO