Abstract: Fonts of characters of an alphabetic and numerical set thereof are described wherein each character of a set is formed from a dot-like pixel matrix and exhibits a predetermined constant and equal number of pixels. Any illegal alteration of the characters of the font set is avoided by forming the dot-like pixels defining a character in permanent fashion as by indentation in the surface of the article to be marked such that pixels cannot be erased, but only added. The pixels within the top and bottom three rows of each character of the font sets form a pattern unique to that character so that the identity of the character may be recovered if a portion of it is lost. A security encryption technique becomes available through the use of characters from two font formats.

Abstract: A set of characters is provided wherein each character is formed by arranging a number of relatively small like characters in a pattern that presents a filled-in outline of the character. Each of the small like characters are printed by a thermographic process to provide a character which protrudes slightly from the media surface thus providing tactile feedback when the character is touched or traced with a finger.