currious would like to know the answer as well. Could it be he also has a solo rig and this is reporting a chain found that way?
I think someone might be faking the slush "signature". I'm not wholly certain how who mines what block is assigned, but have a look at the coinbase:
237246: ��/P2SH/��Q�R 464d/slush/
237270: ֞/P2SH/� �Q � 549bf/slush/
237278: ޞM�/slush/R,�mmY#4�d�O� �g�@? �J�-_h�1q�s�
Additionally, the payout address usually used is 1AqTMY, but the questionable block is 152MGP.
Again, I don't know exactly what's going on here but I see a broken pattern.