It was made by the US based (132nd Street, New York City) company Comet, who were in business circa 1938/39 to 1941, then the war intervened, and they continued post-war under a new brand name (which I think you already know), Authenticast, later also with a factory in Ireland.
This figure is from one of their American War of Independence sets.
The odd shaped base is a Comet products characteristic.
You need to buy a copy of the book 'Collecting American-Made Toy Soldiers' by (the recently deceased) Richard O'Brien. It is a huge 717 page, A4 sized paperback, and well worth its usual modest price.