DescriptionParallel Line Tracer stock no. 1859D made by the Keuffel & Esser Co., (Hoboken), no date, circa 1948-1960. "Xylonite" brand transparent plastic, 1-3/4" diameter, machined holes; stamped black numerals, logo and lettering. With: original printed stock envelope. Enclosed: printed product sheet , 4-5/8" x 6-5/8". Apparently introduced with the 41st edition catalog of 1949. Different items using the 1859 stock number appear in prior catalogs. Product sheet has a 1948 copyright. Front of product sheet has an illustration showing it in use. Back of product sheet has some suggested uses with details of how to use it: In Graph Plotting In Mapping In Railroad Work In Airplane or Ship Design For Cross-hatching As A Lettering Guide In Artwork In Mathematical Analysis K&E had their main office and factories in Hoboken when this item was made.