Campbell Patent Square Stanley 32 1/2 Rule
Robert Campbell's Oct 1 1907 patent (click here for more info) rule attachment to convert any appropriate width rule to a square. Includes a Stanley 32 1/2 rule.

Robert Campbell's Oct 1 1907 patent (click here for more info) rule attachment to convert any appropriate width rule to a square. Includes a Stanley 32 1/2 rule.