Popular explanations of the use of the word "Brown" include that it was a reference to either the colour of the walnut stocks, or to the characteristic brown colour that was produced by russeting, an early form of metal treatment. However, in the case of russeting at least, the Oxford English Dictionary (OED) and Ferguson note that "browning" was only introduced in the early 19th century, well after the term had come into general use. Others argue that mass-produced weapons of the time were coated in brown varnish on metal parts as a rust preventative and on wood as a sealer (or in the case of unscrupulous contractors, to disguise inferior or non-regulation types of wood), an entirely different thing from russeting.