could have been bitcoin-core
Bitcoin core to this day does not support BIP39 or any alternative mnemonic algorithm.
I need a electrum version 0.3 or before like 0.2 but I am not a programmer and can't compile complex programs. I need a complete wallet file as an executable or for use with python.
Have you tried the newest version and see if that recognizes the words you have? As far as I can tell Electrum has kept backward compatibility.
If that failed you may want to start a new issue on their repository to get the attention of the developer who may know more about the initial seed generation algorithm.