This is a watchmaker screw head polisher. This tool is likely over 100 years old and still highly useful today. To the right of the tool are stacked wood cylindrical polishing blocks that hold polishing (lapping) compound. The tool works via a rotational polishing process known as lapping wherein the cylinder on the left holding lapping compound is rotated back-and-forth, not just in one direction, and likewise the screw in its holder on the right is also rotated back-and-forth. This tool can also be used to polish the threaded end of a screw with a lantern attachment and can be adapted for some other polishing uses.