There is an island named Yap in the Pacific Ocean that uses large stone discs as their local currency. The stones can be as small as 1.4 inches to as large 13 feet wide. These stones are referred to as Rai Stones and the physical location of the stone isn't relevant.
Rai stones are made out of limestone and it is unknown when they were first used as currency. As I mentioned before, the location of the actual Rai Stone isn't important, ownership of the stones can be transferred regardless of the physical location. This is critical because some of the stones weigh as much as 8,800 lbs.
The majority of these discs are too large to move and remain in the same place regardless of the current owner. There is one Rai Stone that is at the bottom of the ocean and hasn't been seen in over 100 years and is still considered a valid currency in circulation.
Rai Stones were first created after explorers discovered limestone deposits which were carved into large stone discs. At some unknown point, these discs became a currency and used throughout Yap to this day. Rai Stones are not typically used for day to day transactions due to their value and size.
The value of a Rai Stone is not only determined by the size but by the history of the stone. These stones and their use are quite fascinating and strange. Many of the stones have an interesting history that increases the value of the stone.
While I couldn't find a lot of information about how much Rai Stones are worth, I did see some of the smaller Rai Stones are worth over $6,000 with this one being auctioned off for nearly $14,000.
I highly recommend checking out Vic Stefanu's video exploring the island of Yap to see what these stones really look like.
There is also a Ted talk by Neha Narula that talks about Rai Stones that is interesting to watch.
This video talks about a similar example where a large portion of gold was purchased by France and instead of being transported, it was just labeled as belonging to France. Similar to how Rai Stones are used in transactions.