Here is an example of a Metagaming ad that appeared in the Dragon Magazine. The first thing you will notice is that it isn't a very good ad, from a design perspective. Not that any of the ads that appeared in Dragon were much better.
This particular ad appeared on the back page of the December 1979 Dragon magazine (#32). That was the same issue of Dragon magazine that featured "The Fell Pass", a fan-written adventure, winning the first annual(?) International Dungeon Design Contest.
This particular advertisement is promoting Metagaming's micro-game subscription service. You could become a micro-game subscriber, and have each new micro-game delivered to your door, as it was released. No more running down to the FLGS to see if the latest micro-game was available.
The images around the outside edge of the advertisement are pieces of artwork from several of the micro-games that had already been released, including Ogre, Chitin I, WarpWar, Wizard, GEV, Olympica, and Death Test.