I have already used dumpwallet with pywallet on the recovered wallets I found with a full drive scan. This is a wallet.dat I found in a lost partition by using recovery software. The file won't dump like the other wallets, as I think it is corrupted, and shows as 96kb before using pywallets dumpwallet command. The resulting dumped wallet is only 32kb and says "wallet is encrypted passphrase is correct" but unlike the others it shows only one encrypted private key and nothing else apart from salt and a number. The one encrypted key is a different alphanumeric number to any of the other encrypted private keys I have recovered, so obviously it could be the one I'm after. None of the wallets are usable in the normal way in bitcoin core no matter what command you use as they are corrupted. I have used the passphrase on the other recovered wallet.dats and it shows all the addresses, private keys, mkey etc ie it decrypts the wallets.