Bip39 seed phrase generator https://unsplash.com/@morganvmyg Let's believe It will probably be 10x more quickly than the GFX card above so approximately 2,4M hashes/s. An average attacker will have a handful of this sort of specialised devices. For words that only have 3 letters, there's no 4th letter. By way of https://bookmarksfocus.com/story5885439/bip39-to-slip39-examine-this-report-on-bip39-vs-slip39-https-cutt-ly-uryc5rw7