In 1825, a mysterious double edged sword containing a cryptic code was found in the River Witham near Lincoln in England. The 13th century sword contains an enigmatic 18-letter message running down the center of the blade, and cryptographers and linguists have been unable to crack it. The British Library is now appealing to the public for help in solving this 800 year old mystery.
You may be better asking in /r/askhistory as I gather speculation isn't allowed here. If someone knew the answer with sources then they'd more likely reveal it to the British Museum.
Apologies if this comment is not allowed either.