Date coding on the bottom of every Zippo lighters case is the Zippo Manufacturing Company's way of identifying when a specific Zippo lighter was created, whereas it might be dots, dashes, dates or even how the word "Zippo" is written.
Date coding is a procedure that was adopted by the Zippo Manufacturing Company for quality control purposes. The date coding procedure was first started in the mid 50's when the date codes were stamped on the bottom of the Zippo lighter's case.
Although the original purpose for date coding was for quality control, the procedure became an invaluable tool for the Zippo lighter collector. The date code enables the collectors to determine the age of the Zippo lighter at a glance. This is fun and easy to do because every Zippo lighter since 1933 has some kind of identification on the bottom of the Zippo lighter case.
The Zippo lighters made in 1933 and up till the mid 1950's have "Zippo" stamped in block letters on the lighter case.
A new Zippo logo was developed in the 1940's but was not implemented until 1955. The new logo was a script version of the word "Zippo" and was phased in about that time along with the year coding by the use of dots (.). Over the years, the dating codes has been modified, several times over like for instance in 1966 till 1973 the code was denoted by a combination of vertical lines (), 1974 until 1982 with forward slashes (/), and 1982 until the middle of 1986 with backslashes (\).
Around the late 70's the logo was redesigned again, but not implemented into the bottom stamp until 1980. In July of 1986, lot codes were also being included on all Zippo lighters, showing the month and the year of production. The Zippo Manufacturing Company started featuring at the bottom of the lighter case, on the left side of the logo, the month code in the center, and the year stamped in Roman numerals (XVI).
At the turn of the new century, Zippo Manufacturing Company introduced a new and easier way to recognize the date codes. The letters A-L on the left side of the Zippo logo represents the month that the lighter was manufactured (A = January, B = February, etc.), the year is identified by the last two numbers on the right of the Zippo logo.
As always since 1933, thanks to Mr. George G. Blaisdell, founder of the Zippo Manufacturing Company, the Zippo lighter carries a 100% lifetime guarantee on any problem that might arise with any Zippo lighter.