Captain America Action from 1944 (No Sheild but a Gun?)

80 years ago this year
The differences between the comic book and film versions of the title character in this serial are more extreme
His secret identity is District Attorney Grant Gardner rather than U.S. Army Private Steve Rogers.
The "Super-Soldier Serum" origin is not used.
His famous shield does not appear, replaced by a standard gun.
Despite the fact that this serial was made in 1944, and Captain America regularly fought Nazis in the comics, the Nazis are not part of the story in any way.
His sidekick, Bucky, does not appear.

The reason for the differences appears not to be arbitrary, but that the script for the serial originally featured an entirely different licensed lead character and it was only decided later to replace the original character with Captain America. Film historians Jim Harmon and Don Glut speculated that the script was originally written as a sequel to 1940's Mysterious Doctor Satan, which featured the masked hero The Copperhead. This character was himself a substitution for DC's Superman, after Republic's bid for that character's film rights lost to Paramount, who had a series of cartoon shorts made by the Fleischer Studios, and would later on acquire Republic, as well as distribute a feature-length Captain America film.

The serial sees Captain America, really District Attorney Grant Gardner, trying to thwart the plans of the Scarab, really museum curator Dr. Cyrus Maldor—especially regarding his attempts to acquire the "Dynamic Vibrator" and "Electronic Firebolt", devices that could be used as super-weapons.[