I am not at all sure that these cartridges were made just for the Navy. It is possible, since they are designated specifically for the Thompson SMG. I don’t know if the Brazilian Army had any TSMGs or not. Brazil made a copy of the M3 “Grease Gun” and the Army may have used just those in .45 caliber.
The “Marine Varnish,” though, was not just a sealant, but was also used to identify this ammunition as military property. Commercial ammunition, generally found in calibers 6.35 mm and 7.65 mm Browning (known, but scarce, in other calibers) had red seals, including an all-red bullet. These were exported as well, but drew confusion as to whether or not they were Proof Loads, so eventually, the export ammunition had green seals also, or no seals.
Ammunition of .45 Auto, 7.63 mm Mauser auto, and 7.65 mm Browning calibers made specifically for the Brazilian Navy were headstamped M DAM M (Caliber). This stood for Director of Armaments for the Navy, Ministry of the Navy. Oddly, the .45 and 7.63 mm rounds have no visible seals at all. Bullets are CN FMJ RN. My 7.65 mm Browning “DAM” round has red seals, but it was found in a commercial box with the other rounds having the standard (non-Navy) headstamp.
The Air Force also had some specially headstamped .45s, marked -CBC-MAer-45 ACP-, and has the green primer seal and all green-lacquered bullet. The headstamp Stands for Aeronautical Ministry. There was a later one, very read, with “FAB” headstamp. which I do not have, but believe it stands for “Brazilian Air Force.”
The standard M4 is found in some variations, including dated headstamp, cartridges with no visible seals and a cartridge in a nickeled-brass case with just a standard green primer seal, but no neck seal or bullet coloration at all. There is also a HPT (Proof) round with pruple base and all-purple bullet. Mine came from the factory that produced the M3 SMG copy.
Hope this helps and is of some interest.