I wasn't aware of any single person being in possession of that many coins. I would almost think it was an exchange, but those normally show up with much more than one single wallet. Strange.
I wonder if it's related to an exchange that took/stole/went under several years ago? I lost some ZeitCoin on one back then, can't recall the name off hand, but there's been a few where we were sure someone made off with a lot of coins.