Founded as Plomb, it is presently a division of Stanley Black & Decker.

The company is credited with creating the first combination wrench in 1933.

Proto was founded in 1907 by Alphonse Plomb, Jacob Weninger, and Charles Williams as the Plomb Tool Company, a small blacksmith shop making chisels in Los Angeles.

In 1933, Plomb released what is commonly credited as the first combination wrench.

In 1957, the company began operating as Pendleton Tool Industries.