At first glance, your illustration does not look to be an original Brassard, it is a pity you don't show the rear part - for the only official issue was the one with the Red Cross, the text related to Article 21 of the 1929 Geneva Convention, and the prefix letter and sequence of digits (also stamped on the medical ID card).
Some locally-made armbands may have been manufactured (like the Tabards later) but the risk was that they might have been misinterpreted by the enemy as a ruse-de-guerre, or fakes, for not being provided with the required official Geneva Convention stamps ! I personally think it is very unlikely that non-official issue brassards were ever made available.
You can read about the brassards in our Article : Identification of Medical Personnel, Vehicles and Installations.
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