Making History

I was seeing it only count new projects of mine towards the end. It ignored repeats for sure. But I don't know if that was true from the start.

This is bugged as of 4.0.3a. We were able to rais our completed projects simply by relogging a couple of times until we got the achievement.

Credit towards this achievement is assigned each time an artifact is solved for the first time by a toon in the guild. This new solve by that toon will count as one 'Archaeology research project' credit.
Since any one toon can only solve a maximum of 140 artifacts (including rares), it follows that it would take a minimum of four toons solving almost all possible artifacts to get this acheivement.
In practice of course, it would be far easier to get say, 20 different people to solve 25 new artifacts each. Either way, the guild would still get the achievement.