This bit extension is a new one to me, but the Millers Falls and Yankee models are pretty common. Greenlee was granted a patent for this in 1930, but DATAMP reports that it is “not known to have been produced”. But here it is, and if you need to bore deep auger holes or reach between joist or rafters, this is your tool. You could be the first one on the block to own one by Greenlee. It is in Fine condition.