Unless the fork as had all the decals removed, all MTB forks on the market have their brand, and model prominently displayed, Does it have them?

From the picture, it's a Marzocchi fork, which would indicate it's from 2004-2009 going by Bikepedia, although each year of the Vertex 30 used a different fork model.

As it's a bomber chassis fork, unless you want to pull it a part (and that's not hard), just get some silicone spray, and spray the seals to see it that stops the squeak.