Here are some useful links for dating your Zippo.
New to collecting?
Buyer beware, do not believe the seller (unless a respected collector.) I have seen many examples of sellers falsely claiming a Zippo's manufactured date on well known commerce sites. They justify their false claims saying they are no expert! Selling a Zippo as thirties for example(very rare and worth likely four figures,) when it is only worth two figures! It is a practise I wish the commerce sites would endeavor to prevent via seller guidelines, it is a false claim after all! To them I say here, protect your buyers, trust is important. If the seller is no expert, who are they to date it as the most expensive?
Feeling rich? :-) here is an actual thirties Zippo;