Zippo began putting dates on their lighters after July 1986. The numbers include a date code showing the month and the year of the lighter’s production.
When you check beneath the lighter, you will notice a stamped letter "A-L." This letter denoted the month when they produced with A being January, B February, C March and so on. You will also notice the right side there is a Roman numeral, which depicts the year and it begins with II, which is the year 1986.