Golden Age Origin 
Clay Boone was a traveling gunsmith who carried all his tools in his wagon. The wagon also contained enough guns to arm an entire town. Clay would become the masked hero Gunmaster when he was needed to save the day. His sidekick was Bob Tellub, a.k.a. Bullet the Gun Boy.

Golden Age Appearances  
Six-Gun Heroes #57-83
Six-Gun Heroes #7-8 (promotional comics)
Gunmaster #1-4, 84-89
Danger #18 (re-print)
Outlaws of the West #34

Real Name

Clay Boone

First Appearance

Six-Gun Heroes #57 (1960)

Original Publisher

Charlton

Created by

Dick Giordano

OK, I got everything I could find that is scanned and available on this guy, I hope you enjoy it!