1. An article bearing upon the material thereof one or more identifying words composed of a plurality of letters chosen from an alphabet comprising twenty-six distinctive letters wherein: a. said twenty-six distinctive letters have substantially the configuration shown in FIG. 3 hereof; b. twnety-four of said twenty-six distinctive letters are invertible and each of said twenty-four letters form, when inverted, either the same letter as before that letter was inverted or another letter from said alphabet so that uninverted words may be selectively composed of said twenty-four letters, and said words when inverted, can form either the same words or different words from the uninverted words; and c. said twenty-six distinctive letters, when univerted, are readily distinguishable from one another upon comparison of the characteristic features of each of the twenty-six distinctive letters.