Okinawan/Ryukyuan knife?

[Pitt1999]

After seeking some help on the Nihonto Message Board Forum, some of the details of this knife have been straightened out. It was confirmed to be an Okinawan knife most likely made on Ishigaki Island. A user on there identified the worn down stamp as the character "Ishi(石)", leading to the idea that my example was made on the aforementioned island. It was also discussed on there that at one point there were around 30 to 40 blacksmiths on Ishigaki that were in operation, but now there is only one person left that makes knives like these on that island. I know of one other smith on the main island of Okinawa in the village of Ginoza that also makes knives of this type.