In one shot, Asia Argento's tailbone tattoo is visible. Although tattoos were known to early 19th century Europeans (in fact, they date back before civilization), it seems improbable that Argento's character, a Spanish lady in France, was meant to have a tattoo in a design like the actress's tattoo.
While Ryno is descending the stairs at the opera, an Edgar Degas mural can be seen. Degas would have only just been born in this era.