DescriptionLogarithmic spiral curve, model no. 57 1000, made by Keuffel & Esser Co., no date, circa late 1950s - 1960s. Clear plastic (Luxylite) with engraved markings, circa 8" x 5-1/2". With: 8 page printed instruction pamphlet (stock number S28-1), 5-1/4" x 8" high. For drafting and design. K+E factory was in Hoboken during the estimated period of when it was made. To be researched for more precise date of issue.