Japan - Okinawa Seals?

I am not sure are these some kind of local issues, but more probably some kind of seals used to mark the mail when it passed Okinawa.

These are product inspection seals from the Okinawa Prefectural Product Inspection Bureau.

There seem to have been a huge range of inspection bodies, either regional, like these for Okinawa, or for particular industries, such as ceramics. From the look of those I've seen, they were all pre-World War II.

(I guess the younger generation can't remember a time when 'Made in Japan' meant cheap and unreliable rubbish. These inspection seals were probably intended to try to counter that impression.)

Thank you for the nice observation!