The Shugborough Inscription is a mysterious inscription found on a monument at Shugborough Hall in Staffordshire, England. The inscription has baffled scholars for centuries and is believed to be a coded message from the 18th century. It consists of a combination of letters and symbols, including the
From Wikipedia
The Shugborough Inscription is a sequence of letters – O U O S V A V V, between the letters D M on a lower plane – carved on the 18th-century Shepherd's Monument in the grounds of Shugborough Hall in Staffordshire, England, below a mirror image of Nicolas Poussin's painting the Shepherds of Arcadia. It has never been satisfactorily explained, and has been called one of the world's top uncracked ciphertexts.