As royalflush noted, some guy (me) on head-fi, "claimed that his broken K267 was not repaired under AKG warranty, but replaced with a K712 instead." Yes, that happened. And while I like the K712, a lot, I still went out and found another K267 because I like them so much. The isolation, portability & overall sound signature are what sold me on the K267 in the first place and what I missed with the K712.
Maybe Will can check a few serial...