The Dur-O-Lite Pencil Company was a Chicago, Illinois

Illinois

Illinois is the fifth-most populous state of the United States of America, and is often noted for being a microcosm of the entire country. With Chicago in the northeast, small industrial cities and great agricultural productivity in central and northern Illinois, and natural resources like coal,...

, United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 company that manufactured mechanical pencil

Mechanical pencil

A mechanical pencil or a propelling pencil is a pencil with a replaceable and mechanically extendable solid pigment core called a lead . It is designed such that the lead can be extended as its point is worn away...

s from the 1920s into the 1990s. The company registered the "Dur-O-Lite" trademark in 1927. John P. Lynn

John P. Lynn

John P. Lynn was a Chicago businessman.After serving in France during World War I, Lynn returned to Chicago. Around 1920, he was one of the founders of the Autopoint Company. He helped pioneer the use of plastics to make mechanical pencils. Around 1925, Lynn sold his holdings in Autopoint to the...

 was a founder of the company and was long associated with Dur-O-Lite. Lynn had earlier been a founder of the Autopoint Company

Autopoint Company

The Autopoint Company was a manufacturer of pencils and desk top accessories in Chicago for about 50 years from the 1920s to around 1970. During that period Autopoint sold millions of pencils advertising companies large and small all over the country....

which was Dur-O-Lite's main competitor.

See additional information by Robert L. Bolin:
http://www.unl.edu/Bolin_resources/pencil_page/mystery/SPIRAL_GUIDE.HTML

In 1993, Dur-O-Lite ceased all manufacturing operations.