Bip39 private key recovery tool http://www.video-bookmark.com/user/tucanewhmt Although it utilizes BIP32 approach you could even now import BIP39 seeds into Electrum wallet. Also besides BIp32 There may be BIP44 version which some wallet use for the generation of seeds. For words that have only three letters, there isn't a 4th letter. https://bookmark-group.com/story5880158/bip39-c-the-smart-trick-of-bip39-wallet-that-no-one-is-discussing-https-dzen-ru-bip39-phrase-com