Is bip39 safe https://ameblo.jp/generate-bip39brooks/entry-12913353546.html While it makes use of BIP32 strategy you can even now import BIP39 seeds into Electrum wallet. Also besides BIp32 There may be BIP44 Model which some wallet use for that era of seeds. For words that only have three letters, there isn't any 4th letter. https://bookmarkinglive.com/story21052482/bip39-one-a-simple-key-for-bip39-github-unveiled-https-x-com-tundra838554