1. letters represent the production month: a stands for January, b stands for February, and so on. These letters are usually located to the left of the bottom sign.
2. Numbers represent the year of production: usually two Arabic numerals, for example, "14" represents the production in 214. These numbers are located to the right of the bottom sign.
3. The bold part in the middle is the trademark of Zippo.
4. The bottom line is usually the origin information. For most Zippo lighters, the words "bradford.pa" will be printed here, which is the abbreviation of Bradford Town, Pennsylvania and the location of Zippo's headquarters. In addition, "MADE IN U.S.A" stands for made in America.