Darick,
It's the Pen Maker's Guild. Though characterized differently by different people, it's a group for which entry is obtained by submitting a pen or set of pens. The submitted pen(s) are reviewed by several "elders" who critique it/them on a variety of criteria. Obtaining entry is not trivial by any means - the pen(s) must basically be be exceptional all around. There aren't TOO many members, though their ranks are growing. It's a huge recognition of the caliber of pens Lou, and the other members, make. We're lucky enough to have several PMG members who also regularly participate here, and I know I've learned a lot from them all, and especially Lou (we meet in person fairly often).
Check out http://www.penmakersguild.com/ for more info.