I'm looking at my 6Gv2 and it has the same marks as well. I believe it is just an artifact from the molding process for their caps. If it really bothers you, they are the same profile as the Filco caps.
Here is a picture of some of the top row keys on my 6Gv2.Show Image(http://imgur.com/OenN9.jpg)
Molding marks. Even Topres have them if you look hard enough.
My advice is to turn the keyboard around.