What I like about this is it evokes the real window cards Houdini used on his final tour. But before you think this was deliberate, I don't believe these Houdini window cards were even known in 1976. I believe the first ones were discovered in the 1980s. So the production somehow channeled the past and future. Kind of freaky.
Just to round things out, the only other poster mockup in The Great Houdinis is the large banner used during Houdini's pier jump. The typeface seen here is the same as seen on Houdini's "Europe's Eclipsing Sensation" posters.