Might be a 'white box' version. The 6D + 24-105L kit costs $500 more than the 6D body only. Lots of retailers break apart those kits and sell the lens (which comes in a white box inside the kit) separately.
It's likely a White Box version, as neuroanatomist pointed out. The "white box" is simply a kit lens that came with another camera that the retailer decided to sell separately. The lens is in a "white box" because it was shipped in a bigger retail box with the camera body. Like anything else, just make sure the lens is new, unused, and has the appropriate USA warranty.
FYI, I purchased a new White Box 24-105 a couple years ago for $899, so this is a good deal, provided the caveats I mentioned are satisfied. It looked just like the picture above.