The Master Key - 1945 - 6/10

Universal serial set in 1938, before WWII.
Secret Nazis and Nazi sympathizers plan to buy up all the US manufacturing companies and corporations they can.
That way, once war starts, they will own the States.
To accomplish their task, they need money - lots of it.
Fortunately, they have copied the “Orotron,” a device that can extract an endless supply of gold from sea water.
Combating this conspiracy is one FBI agent, one police detective, and a plucky female newspaper reporter.
Luckily for them, there is an empty theater hall nearby, filled with juvenile delinquents who don’t like Nazis, either.
Fast paced cliffhanger with fairly good twists - the usual cheats, nice cast, inventive plot.