my guess would be a wood working tool. Cutter or chisel would go into rectangle grove,then then material (most likley Wood) would be centered with the thumb screw on top,then start turning by Hnad to turn out a perfect circle.
Definatly a circle cutter of some type.modern day tools dont resemble a heavy hand turned device like that for we Have power tools to do the work instead of muscle power.
circa late 1800 my guess
not a very good example But here goes anyways
http://farm3.static.flickr.com/2428/3887347590_c019d6eddd.jpgBut maybe that help Stir up the Cobwebs & Give You a real ID