This series of rulers were made by Lufkin United States in Michigan. Also known as zig zag rulers, they were common until the 1940’s when spring loaded retractable started being made. This extension ruler has brass hinged joints that are freely moving. Ruler is 6 feet or 72 inches long with graduated markings on both sides of the ruler. All joints tight and ruler is accurate when compared to a modern tape measure . Folds up to a 8 inch long, 2 inch tall and 5/8 inch wide package. It has been used and shows use commensurate with its age and purpose. The markings are clear but it does have a patina. The outside end starting at 1 inch/ other side 72 inches has a brass cover as well as a brass scale in the middle of the ruler from 1 to 7 inches. This is unique and possibly puts its manufacture date as in the 1920’s making it over a 100 years old.