Death at Victoria Dock - S1-E4
Character mistake: Fisher refers to some characters as speaking "a Slavic language." The characters are Latvian anarchists. Lettish (aka Latvian) is a Baltic language, not Slavic.

Starring: Essie Davis, Ashleigh Cummings, Hugo Johnstone-Burt, Nathan Page
Death at Victoria Dock - S1-E4
Character mistake: Fisher refers to some characters as speaking "a Slavic language." The characters are Latvian anarchists. Lettish (aka Latvian) is a Baltic language, not Slavic.
Factual error: The snub nosed revolver used by Miss Fisher, a J-Frame S&W, was not produced until 1950.
Other mistake: Miss Fisher takes a handwritten phrase in "ancient" Hebrew to one of the main characters to be translated. The writing is actually in cursive Hebrew and is properly written. While performing the translation however, the "expert" translator holds the writing upside down. He also follows the writing with his finger from left to right. Hebrew is written from right to left. (00:32:00)
Suggested correction: When reading Hebrew upside down, tracking from left to right is actually the correct way. Of course, reading this way in the first place is extremely weird, at least.