The process of letterpress printing remains essentially unchanged since Johannes Gutenberg “invented” movable metal type circa 1445 (baked clay type had been used in Korea centuries before, and in China even earlier). A cast iron press holds individual lead or wood letters in place, within a frame called a chase; the type is inked by hand or by the action of the press; the inked type is then pressed into a sheet of paper. You can often feel the three-dimensional impression, which is also visible as a kind of halo surrounding each letter. The amount of impression is a matter of personal taste, and is also governed by the kind of paper used and the nature of the type. (Elderly or rare type is especially jeopardized by a hard hit; photopolymer plates are not bothered.)