The prop for Mata Hari's ring is an authentic period signet ring.
Jonathan Demers also performs two additional uncredited roles: the guard who comes to collect Mata Hari and the voice of the captain of the French firing squad.
Actress Debra Leigh Siegel consulted with a number of people fluent in Dutch to develop the accent she used for the character, but had to adjust some of the pronunciation to be more inauthentic, as the actual pronunciation of some words would have rendered her lines too difficult to understand.
Maureen Vlaco invented a back story for her character where she and Frank ( Jonathan Demers ) were having an affair. She would loudly sniff his hair after she hugged him.
The period pictures of Mata Hari used throughout the film, including on the book jacket, are all pictures of Debra Leigh Siegel, dressed in period costuming and jewelry. No digital manipulation was performed on any of the images apart from desaturating them.