According to XYZ Collectibles, there are many old National Geographic magazines that are worth money. For example, as of 2014, the January 1902 issue of National Geographic is valued at $816.50.
The worth of a magazine is not determined by date alone, although typically, the older the magazine, the higher its value. However, the oldest magazine is not worth any money if it is not in good condition.
While some wear is expected, an old National Geographic magazine must not be torn, scuffed, water marked or otherwise damaged to be considered a collector's item. Collectors, auctioneers and antique dealers are a good source of information about the value of old magazines.