An interest for further research of mine are the revolutary groups from the war of independence of Indonesia. Here a very rare armlet for the Special Police as it existed only in 1945/46.
Text adapted from Wikipedia:
Formed in late 1945 as a special police corps named Pasukan Polisi Istimewa (Special Police Troops) with the task of disarming remnants of the Japanese Imperial Army and protecting the chief of state and the capital city. Under the Japanese, it was called Special Police Unit (特別警察隊, Tokubetsu Keisatsutai). It fought in the revolution and was the first military unit to engage in the Battle of Surabaya under the command of Police Inspector Moehammad Jasin.
On 14 November 1946, Prime Minister Sutan Sjahrir reorganised the Polisi Istimewa into the Mobile Brigade (Mobrig). This Corps was reconstituted to suppress military and police conflicts and even coups d’etat.
On 1 December 1947, Mobrig was militarized and later deployed in various conflicts and confrontations like the PKI rebellion in Madiun, the Darul Islam rebellion (1947) etc.
So far I have not found any images of similar armlets being worn and only one other example of Polisi Istimewa in the collection of Museum Bronbeek but that has a very different form and look! My version looks quite a lot like the Japanese armlets that were worn in Indonesia during WW2.
If you have more info please let me know!