Notes: "This beautiful little thread counting magnifier or microscope is designed for the textile trade, but could be used for measuring anything. The microscope, which has all of its optical elements in one small tube the size of a small microscope eyepiece, is adjustable for focus. Magnification appears to be roughly 10x-12x. The microscope is mounted on a lead screw that is turned with a thumbwheel on the left to traverse left and right. For quicker traverses, you can push the lever on the top, which disconnects the microscope from the lead screw, and move the eyepiece manually. For taking measurements, or counting threads, there is a revolving three-sided ruler with four different scales. One scale is 1"" long, divided into tenths of an inch. Another is 1"" long, divided into quarter inches. The third scale has two sections; one is 1 cm long and divided into mm, the other is a Paris Inch or ""pouce"", (marked ""F"") divided into 12 Paris Lines (""ligne""). A Paris Inch has a length of approximately 1.066 modern inches. While the Paris Inch is no longer used, the ligne continues to be used by French and Swiss watchmakers to specify the diameter of watch movements. Also, the ligne is still the standard unit for measuring the width of men's hat bands. "
