Here is another whats-it

It attaches to a brace and there is a chuck for some type of boring bit. My initial thought was an auger and may still be that but the chain is throwing me. It is obviously there to allow drilling into irregular shaped objects. Possibly for drilling into pipe in which case one wouldnt use an auger but a bit suitable for the material being drilled....
 
It is a brace attachment and is intended for drilling large beams. The chain wraps around the beam and as the brace is turned, the chain is pulled toward the brace keeping it tight and applying pressure on the auger bit as it drills the hole.
 
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