Forget suggesting that "343 Industries" was the name of some Halo-related studio at Microsoft. It's a fact, with the group officially revealing themselves as part of the Halo anime announcement.
Interestingly, 343 are described as a "division" of Microsoft, not a development studio. Which makes sense, since having spoken with 343's creative director, former Bungie man Frankie O'Connor, this LA Times piece says the division "oversees all Halo products". Not just games. Everything. Games, comics, toys, cartoons, the works.
That's unique for Microsoft, as it makes 343 an entertainment division. Not hardware, not software, just entertainment. Wonder what that means for the long-delayed Halo movie project?
Obviously, since this information was part of an LA Times article and not an official announcement, we're sure there's more details to come about this new group in the days to come. We'll update you when we hear more.
UPDATE - Here's Microsoft's official "bio" for 343:
343 Industries is the publisher of the blockbuster "Halo" series of videogames and, as part of Microsoft Game Studios, oversees the "Halo" franchise, including novels, comics, licensed collectibles, apparel and more. 343 Industries is home to world-class developers working on future "Halo" projects, including "Halo Legends" and Halo Waypoint, as well as partnering with renowned developers such as Bungie LLC and Robot Entertainment to produce "Halo" games for Xbox 360 and Xbox LIVE.