Thanks Mike!
I have not found any period documentation on a piece like this existing, however this piece shows clear signs of use between the name in the interior, as well as the pin holes above the "D" in "BDM" for attachment to the uniform. Holes are visible in the reverse as well to close the back side of the armband. Although a specific patch was used on the sleeve, I would take a stab at saying this piece likely was worn by those who were not traditionally medical service, but were later in the service as the war progressed. The material used seems to be an oil cloth type construction, not something I've seen a fake made out of before.
