In the early truck years, the available rubber was not the quality as later. GM realized that the constant use on the pedals on a work truck would soon cause a rubber pad to fall to the floor. Then the driver would have a smooth metal surface that was polished daily from shoe contact. Not good.
To keep the driver's foot from slipping on them, these pedals are equipped with small "bumps" in the metal. This gives many years of use by the soles of the driver's shoes. Ingenious!
These bumps are molded in the pedals during production.
