Penal Code § 2882

It is hereby specifically provided that any article of prison-made goods, wares or merchandise, as described in the preceding section, may be labeled by the attachment of a label not smaller than four inches long and two inches wide, upon which is printed the words “Convict-made” in plain, bold letters followed by the name of such penitentiary, prison, reformatory, or other establishment in which the goods, wares or merchandise were made; provided, that in the judgment of officials charged with the enforcement of this article such prison-made goods, wares or merchandise can not be legibly, conspicuously and indelibly branded, molded, embossed, stenciled or labeled as provided in said preceding section.