I did some digging and found info on how to mine back then in archived forum versions. Block rewards were definitely 50 BTC, so you couldn’t have mined that many without receiving some elsewhere.
Pywallet does, but I'm not sure if wallet.dat from 2010 used Berkeley DB yet. You might want to check the whole discussion. Slush’s mining pool did exist, and Gavin created a faucet in 2010 too.