I recently purchased an Atlas metal lathe along with an assortment of machinist's tools. This mounted dial indicator was among them, but I can't figure out what this is intended to measure. It is marked "Federal" and the model number is 57B-3-R1The dial rests on a very thin needle and is operated with a small lever that can be seen on the left side of the dial. The base is very heavy cast iron and it seems like a very precise tool. It measures in increments of .0005 inches. I would appreciate any help on this, thanks.