The taxpayer purchased in bulk lots, by the pound, old and worn-out motor vehicle tires and put them through a process of repair, treatment (including being pressed and partially cooked in a boiler) and retreading, and sold the retreaded tires. Throughout the process the sidewall of the tire was not dismantled or destroyed, the numerical identification of the original tire was not destroyed, the name of the manufacturer of the original tire was still clearly marked upon its sidewalls.