This is really a misnomer, as there never was such a pigment known to the trade. A one time student of applied chemistry, long since deceased, suggested this formula to some one in authority and it has been among the United States Navy Department specifications for some 22 years as follows:
40% zinc oxide; 5% red lead; and not less than 20% sesquioxide of iron. Balance to be composed of the gangue occurring with oxide of iron in nature. Must not contain lime in any form. In other words it may consist in the pigment portion of 40 parts by weight of American zinc oxide, 5 parts dry red lead and 55 parts of mineral brown, such as will give the shade desired by the service. Usual proportion of pigment in the paste 78 to 80%, raw linseed oil 20 to 22%.
Waterproof Compositions for Fishing Rods and Baiting Articles of Wood.