"Okinawa Rosetta Stone"

...as it's sometimes called. Except the point of the Rosetta Stone is that it has two languages (and three scripts) on it thus enabling the decoding of hieroglyphics. "Oh, shut up, beardy!"

There's a number of dotty theories about early civilisation in this area, especially the southernmost island of Yonaguni, where some believe there's an abandoned underwater settlement that is evidence of a lost civilisation. Graham Hancock et al...

It's quite possible. It depends what you call advanced. Certainly the Yonaguni site is intriguing, but it's not impossible for the formation to be entirely geological in origin.

This stone is one of a number found on Okinawa island in 1952 (?). The museum staff claimed both its meaning and date of origin are unknown. These objects could be ancient or they could be more recent. On the Japanese mainland there are a number of supposedly ancient Shinto texts that use unique writing systems which are in fact recent of recent invention. Such texts are used to support the idea that Japanese culture was at point literate prior to the arrival of Chinese writing systems from the mainland and, thus, Japan truly is the land of the gods. Blah, blah, blah.

Might something similar be occurring here? Do these stones date to a period prior to the arrival of Chinese culture? Is someone having an archaeological joke? No idea. They're certainly beguiling.

www.wonder-okinawa.jp/024/english/hikiage/sekiban/rozetta/

morien-institute.org/interview2_MK.html