Character mistake: When Juliana puts the film on the projector she loads the reel backwards.The film is supposed to drop from the front of the reel, not the back.
Factual error: The kaishakunin decapitates the officer completely. Traditionally, the kaishakunin should perform dakikubi, leaving a small piece of flesh attached while severing the spinal cord and other parts of the neck so the head does not fly off. The kaishakunin in the show did not attempt to achieve this at all. (00:21:15)
Other mistake: It's 1962 and in this reality the Nazis and the Japanese empire won WWII, therefore the United States, Europe, Russia lost. Africa is enslaved. The Japanese detectives go to a suspect's house who turns to be a Nazi soldier who shot the Japanese emperor to instigate a war between the two nations. The Japanese detectives locate a Russian made SVD-63 aka Dragunov, 7.62x54r caliber. How could Russia be making weapons if it was occupied or annihilated? Under these dictatorships weapons are banned. (00:07:30 - 00:09:30)
Revelations - S1-E4
Continuity mistake: Frank is at the Japanese emperor's event, and he pulls out a single action revolver with the hammer already down, a few seconds later as he's about to raise the revolver, the hammer is somehow up, and he begins cocking the hammer to make the gun operational. (00:49:40 - 00:50:20)
Continuity mistake: The officer committing seppuku is seen drawing his blade, and the katana of his kaishakunin is still sheathed. He grunts as he is about to thrust his blade, and the kaishakunin is now holding his katana in the air, ready to behead the officer. When the officer thrusts his blade into his body, the kaishakunin has a sheathed katana again, just about to draw. (00:21:05)
Factual error: In the transition shot showing Hobart Building in San Fransisco, items not belonging to the scene are visible and have not been edited out. These items include; modern phone numbers, web addresses for several companies and educational institutions, satellite dishes and American flags. (00:24:10)
