If there is a patent number on the lighter, you can check the Patent Chart to see when the lighter was first patented, which at least tells you the oldest date a lighter could be, since it could have been made anytime during the initial patent period. Another method is to find data on your lighter in a price guide , if you're lucky. But many of the price guides don't indicate years. These ads, like patent dates, may not give you the exact year when a lighter was issued, but you at least know when that lighter was in use.
Case is flat-bottomed with square corners.
Windscreen has 16 holes and cam support is part of the windscreen. Case is flat-bottomed with square corners. Case is flat-bottomed with square or rounded corners. Still flat-bottomed, but corners are rounded. Bottom slightly rounded, corners rounded.