1LG9NweYZkmfaKW6XyLcB3uLhqR73WMCmv via The ∑ Number Game (archive)
and
1MsXYJikZmCaPgzTHGAMmjLbP9D7QRJ8E5
1Eh3JfsScTThANXZByTjno8PSJrHEtmB6j from the winner's transaction: tx (being from MtGox)

1Gdc8pDDemYFr5zTRs4bwNsVurF8dSxZHw from Christmas Auction IRC and address history

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Gonna need a signed message.

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WalletExplorer yields these results:

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Or perhaps a signed message from the key used here: https://bitcointalk.org/index.php?topic=83059.msg5288700#msg5288700 (archive)
Or this one, if it's different. https://bitcointalk.org/index.php?topic=61080.msg717433#msg717433 (archive)