This doesn't correspond exactly with any scheme on the IWSG Colour-mark Online Database. The closest (but unlikely) match is a Canadian project which uses two white three character engraved flags on the left tibia, metal on right tibia, contact is:
[email protected] Worth checking if they know of a similar scheme to theirs. Just wondering if any of your original images might be sharp enough to show part of the country scheme on the metal ring, which would help.