Metal Tag attached to Rank Insignia

[Ryoyo]

I was looking at this button-on rank tab and wondering about the tag attached. If I had to guess, I'd say it could be a end of war period ID tag for Japanese soldiers being repatriated. ("JP" = "Japanese Prisoner" or just "JaPan"?) Or maybe something more mundane. If I saw the tag by itself I wouldn't have given it a second look, but with the rank I assume it's military related.

[ghp95134]

I would have thought "J[apanese] P[risoner]" as well. Isn't that disk an Australian dog tag blank?
I'm thinking the good captain was an Australian POW.

But just a guess!!!

-- Guy