A Study of Safety Markings of the Model 21
early model 21 standard grade, thoes with plan walnunt stocks woere not con
TOBIN BRONZE - True Brass1
This is an alloy of copper and zinc. Additional elements, such as aluminum, lead, tin, iron, manganese or phosphorus, are added to give the alloy specific properties. Naval rolled brass (Tobin bronze) contains about 60% copper, 39% zinc, and 0.75% tin. This brass is highly corrosion-resistant and is practically impurity free.
Brass sheets and strips are available in several grades: soft, 1/4 hard, 1/2 hard, full hard, and spring When working with lead, you must take grades. Hardness is created by the process of cold roll- proper precautions because the dust, fumes, or ing. All grades of brass can be softened by annealing at a temperature of 550°F to 600°F then allowing it to cool by itself without quenching. Overheating can destroy the zinc in the alloy.
1 The Navy Advancement Center