What do you mean by digging up an old master key? Is it the password/passphrase of the wallet app?
You cited "Schildback.wallet", you are probably referring to the Bitcoin Wallet app (Schildbach Wallet) , in this wallet, the backup is done by exporting a file encrypted by the user password, is this password you are referring to, right?
Also, if you have added a PIN CODE to protect the wallet from unauthorized spending, even if you manage to decrypt the backup file (e.g Bitcoin-Wallet-Backup-2014-11-15-15 28), you need to use Bitcoinj to decipher the wallet file pin to export private keys.
I'm not great with the old stuff and it was originally with schildback.wallet. All the GitHub data is there, but need some assisatnce to decrypt it and check it.
Do a run down on this thread first:
[HOW-TO] Export Bitcoin private keys (in WIF) from Bitcoin Android (schildbach)See if anything in the OP and replies look similar to your "
Master Key" and other files as your post suggests that it's encrypted.
Also, that's posted in a dedicated board for Bitcoin Wallet for Android so try to search the board and you may find a thread or two with similar issue that was solved.
If nothing helps, you should describe what you have in detail like providing "
not-actual-examples" and the feasibility of decoding it (
if you know or at least have an idea of the password).
There are several related topics about decoding the backup of this wallet, unfortunately it's difficult to decrypt, it is recommended to install the Bitcoin Wallet application for Android again and try to decrypt there.