How can you tell quality of Zippo lighter?

Dating Your Zippo Lighter Valuable information on the bottom of every Zippo windproof lighter can help you determine its date of manufacture. Starting in the mid 50s, a date code was stamped on the bottom of every Zippo lighter made. The original purpose was for quality control.

Are there fake Clipper lighters?

The counterfeit lighters found locally looked like Clipper lighters. But just by looking at the lighter consumers can tell if it is genuine or not. Genuine lighters have a plastic ridge inside the top on either side of the striker, counterfeit lighters dont.