I recently acquired this old brace, trying to learn more about what it is. It is all steel, no wood. From what i have found so far, it is similar to a Jeremy Taylor brace with a spring catch for the bit, in the Scottish pattern, and dates to around 1850. There are no markings. I believe Scottish pattern applies to the hex shaped frame. The sydnassloot site has a picture of an identical tool, but with no additional information. The one difference mine has is the washer under the head. I “think” the washer has been added because the retaining pin looks like it might have been replaced … one end is perfectly flush and almost invisible, the other end is slightly mushroomed … visible in the picture.
 

You might also check to see IF that hole in the side of the "Chuck" is threaded?    Maybe a thumbscrew USED to reside there?

Doesn’t look like it, not even any evidence of stripped out threads.  There is a spring clip that catches the notch in the bat wing style bits.   

Missed this post. No help  Ed, but very cool brace plus the bit. You find some treasures out there in Virginia.