for all known pool wallet addresses of 50BTC. Most interesting transaction is the following one, from March this year, where 45,000 BTC were transferred from the address used as the cold wallet for 50BTC to some new address.
However it looks like the owner of 50BTC did have quite a mining farm himself and already did mining on other pools before 50BTC was created, I cannot judge how much of these 45K BTC does belong to the pool owner and how much belongs to 50BTC customers.